To get this trophy simply load up the map 'Crash Cove' and around the first corner you will see a large puddle on the right-hand side. You must drive through it and towards the land on the left that is too high to reach by simply driving to it.
Towards the end of the puddle there is a bump that will force you to hop (hence the achievment name) and at that time you must trick jump to reach up onto the shortcut.
I have created this video to help:
Hope this helps.