If you installed with the Aristois installer from aristois.net it should work out of the box. Make sure that you installed it to the correct Forge instance that you are launching. You should be able to press the right shift button on your keyboard to open the Aristois mod ui. Just tested it on my end and it seems to work without any issues.
If you are unable to open the mod menu with right shift, please send your log file by starting the game and then closing it after its fully loaded. The log found in .minecraft/logs/, called latest.log
If you have any other Forge mods installed, remove them to see if that resolves the issue