Emulation is pretty simple, I use VICE which also emulates other Commodore 8-bit’s such as the C64. From the Vice website …
VICE is a program that runs on a Unix, MS-DOS, Win32, OS/2, Acorn RISC OS, BeOS, QNX 4.x, QNX 6.x, Amiga, GP2X, SkyOS or Mac OS X machine and executes programs intended for the old 8-bit computers. The current version emulates the C64, the C64DTV, the C128, the VIC20, almost all PET models, the PLUS4 and the CBM-II (aka C610).
The important part is knowing what RAM set up a game requires. The Vic 20 came with 3.5K of usable RAM by default and all unexpanded games will run in this mode. There were also RAM expansions released in various sizes and many games took advantage of the extra memory. Unfortunately a game will only run on the RAM configuration it was created for. The most common options were an extra 3K, 8K and 16K of RAM so choose the size from the Settings->Vic Settings… menu.

Vic Settings... for RAM options
All the games on Vic20Gamer have information on the RAM configuration and usually how to get the game up and running in the emulator. However most games can be started with File->Autostart disk/tape image… after you set up the RAM so stick with this for best results.
Have fun!