Welcome to the forums. First, make sure you have a good battery and make sure it's fully charged, as a bad or low battery can cause shifting problems.
When you first turn the key on, does the gear position indicator blink? If so, count the number of blinks, as this is a trouble code.
Most 4-wheeler problems are caused by a loose nut connecting the handlebars and the seat!!
You only need two tools in life -- WD-40 and duct tape. If it doesn't move and should, use the WD-40. If it shouldn't move and does, use the duct tape.