how to get more fps?

The best way to increase performance in a game would be through upgrading your hardware.

If this is not a feasible option because of how stupidly expensive that can get, I would recommend doing the following if you haven't already:

1. Close pretty much everything but the game you're playing. Unless it's entirely necessary, don't have it open. This will just eat into system resources that could be used for whatever game you're playing.
2. Edit your settings in-game. If you're getting a low FPS, try decreasing render distance, texture quality, or any other graphics settings. If your computer is struggling to run it with settings on high, tick them back a little bit.
3. If you're playing on a laptop, make sure you're running on performance mode instead of battery saving.