How did you fit it? I always put it in 2nd before removing the old one or you have no idea where the gears are?
Should be a procedure in the instructions. But basically putting it in 1st and 2nd repeatedly while partly tightening the bolts allows the gear lever to run along the side of the gearchange guide. Then go for 3/4 check they are there then check for reverse. If gears dont appear, slacken the bolts and wiggle again. If they still dont appear , then check and possibly replace the shift rod bushing, the gearbox nose cone coupler and maybe the ball in the nose cone of the gearbox. All things that usually contribute more to poor gearchange than any gearshift lever.