Here`s how I do it, being I don`t have a tool to install it either. First I use a file to deburr the end of the crank snout. Next I used sand paper to sand down any high spots. Then I clean the crank up with carb cleaner, checking all the passages in the process. When the crank is clean I use a piece of steel pipe, not much different than what would be in used in a house or business. With a screw on cap on the end of the pipe, I ease the gear on, lube the surface, then use a 1 hand small sledge hammer to drive it on. In the past I`ve also used a piece of exhaust pipe I had laying around. I`ve seen some guys use a hammer to drive it on, and a broken or cracked gear would be the result.
You keep working on it till you can slide it on by hand! If you don't, and miss the keyway, it's going to be a pain getting it back off to try again. It should be JUST loose enough to go on the crank and over the key.