Fisher's step by step guide on how to bunnyhop
1. Lean back and bring front wheel off ground
2. Propel yourself forwards once wheel has cleared obstacle/reached desired height
3. Scoop rear wheel off ground by pushing back on your pedals with your feet
4. Don't stack
Start out by bunny hopping over a bottle or a crack in the concrete and move up to larger objects, such as a cardboard box so that if you don't clear it, no harm done.
It takes a bit of practice at first but you will get the hang of it, easier to start out on a bike that is easy to manual.
Plenty of videos on youtube by the way. Dont know how informative you want them but there isn't much to it, just practise.