First be sure you have well same version of FPse then same game file and bios file scph1001.bin
You must be connected to the same network by using wifi, A good 5ghz connection is necessary to get fast and smooth result
Next on the first device open FPse then go to settings and advanced settings then Multiplayer and PS link cable then choose Player One then run the game you want to playe (see supported just below)
On the second device do the same but choose player 2, normaly FPse should be able to find your first device then run the game simulatenously.
Follow instructions just below to play after.
Here is a list of the games which currently work with FPse in PS Link Cable emulation mode:
1) Andretti: the player 2 is pressing first the PS link mode and the player 1 after, then the loading time is long but it works great
2) Armored core: it works well
3) Armored core, Master of arena: it works well
4) Armored core, Project phantasma: it works well
5) Ayrton Senna Kart Duel: it works well
6) Bogey Dead 6: it works well
7) Burning Road: Player 2 press Link mode then immediatly Player 1 too or game won't start, it works great
8) Destruction Derby: it works well
9) Doom: it works well
10) Final doom: it works well