After installing the mod, you can go in search of a UFO that crashed and fell off the coast of San Fierro. The location is marked on the map.
Installation: move files from the "UFO" folder to ModLoader. Also, using any text editor, open the GTA.dat file (located in GTA San Andreas / DATA) and write these lines:
IDE modloader\ufo\Map\ufo.ide IPL modloader\ufo\Map\ufo.ipl COLFILE 0 modloader\ufo\Map\bufo.col
Also, in the game directory, you need to install Limit_adjuster, if you don't already have it (it's in the archive).