Superjumps are marked with blue cones, there are 50 in total across the map. Simply land 5 of these without crashing or falling and the achievement will unlock.
Superjumps are easier with a lot of boost as the gaps are usually longer than with normal jumps, so a stunt car is recommended for building speed.
If you want a guide to all 50 superjumps, IGNs guide is pretty handy.
https://www.ign.com/wikis/burnout-paradise/Super_Jump_Locati...