My togepi is at level 32 and it is not evolving so I need help to get it to evolve to do the pokedex.
Togepi will evolve after it's levels up with a happiness of at least 220. It starts of with a base happiness of 70 and here is a list of ways a Pokemon's happiness can increase or decrease as well as all the quotes from a Pokemon happiness checker.
A happiness checker will determine the happiness of your Pokemon and will say one of several things depending of a Pokemon's level of happiness. You can find the happiness checker in Platinum in Hearthome city at the fan club with one of the Pokemon fans being the happiness checker. Source
Edit: I also wanted to add that once you evolve Togepi into Togetic, you can further evolve it into a Togekiss with a shiny. Here are the places you can find a shiny stone in Platinum.
Hope I helped :)