In order to get to Espelunguère from France, start from the town of Oloron Ste-Marie and follow the road to the spanish border, south, all along the Vallée d'Aspe. Turn right just before the french entrance to the Somport road tunnel and follow the previous instructions.
From the parking lot at Espelunguère, start walking (roughly) south-southwest. The beginning of the path is clearly marked by a big pannel informing about the regulations to be enforced in this National Park. This first section of the climb is marked by three parallel paint bands in rocks and trees: (left to right) white, red and white. These are the markings of the HRP (Haute Route des Pyrenées - High Route of the Pyrenees). It is a small path at first, winding through the forest and by the charming cascade of Espelunguère.. In about fifteen minutes you shall get out of the forest and into the pastures of Espelunguère . To your right you will see the dirt road coming up from the parking. This road shall be your main lead for the moment. You will have to follow it uphill (meaning climbing the slope to your right), but it's not necessary to walk along the whole road. It winds several times to reach the forest north of your position, and therefore it would suffice if you just cut across the road walking uphill. In the last crossing (when it turns obvious that there is no more road uphill, just follow the road to your right and into the forest . At the very end of the road there is an obvious path going ahead, marked by the HRP paintings.
Following this path will take you out of the forest in no longer than fifteen to twenty minutes, just by the side of a dirt road. Follow this road an in an additional five minutes you will find yourself in sight of the hut called "Cabane Grosse de Borce". The path goes on uphill to your right (east-northeast) towards the Col de Lapachouau, turning around the ridge to the north. To the other side of this ridge there is a small valley with a hut and a short walk to another small col. The huge pastures of Banasse await you behind that col. The only thing to be done shall be to follow the paint marks of the HRP to reach the lake ("lac") of Arlet and its neighbouring hut. Get going to the nearby Col d'Aillary (visible in the left background of the picture), a notable viewpoint over the Valley of Aguas Tuertas. Once you get to the Col you shall be standing in the very border between France and Spain. This is the moment to reach the top of nearby Pic d'Aillary (to your right, grossly northwest).
The following step is to turn left (south-southeast) to start walking along the ridge towards the summit of Arlet. In some minutes you will have to make a short crossing over the french side of the border, with a small couloir covered by scree behind you. If wet, it might be a delicate point of the route, but the rest of the route is basically a nice walk with only two steep slopes. These slopes might call for a little bit of grade I climbing (just placing the hands on the rocks) but they are not difficult. Just follow the ridge, falling if necessary to the spanish (right) side and you will be on the summit of Arlet in some thirty to fortyfive minutes.
Obviously, coming down by the same route is possible. I will nevertheless tell you about the round trip that will take you back to the "Cabane Grosse de Borce". Keep following the ridge southwards, it's an easy walk through grassy slopes. In some fifteen to thirty minutes the hike shall place you at the summit of Arri, over the Col de la Countende. It's possible to go down directly to the Col, but it's a steep slope covered by grass and scree. Maybe a little bit too impressive for some. A somewhat easier descent can be done walking down towards Spain (to your right, grossly west-southwest). That way you should be able to come down to the altitude of the Col and afterwards walk back to the border to join anyone coming down the hard way. During this descent, please remember that you must always tend towards the Col and look for the easier steps through the rocky bands all around the place. Be careful, as some of them might mean a little bit of climbing down (which we considered to be a grade II). Anyway, once you get to the Col all that will be left shall be an easy descent towards France and the Cabane Grosse de Borce in order to find yourselves on the ascent route. Just take the path going to the valley of Espelunguère (leaving the dirt road to your right scarcely fifty meters after you leave the hut, remember the HRP paint marks) and enjoy the rest of the trip.