Adventure Level 1: Poe To The Rescue - Trash Compactor
It's worth getting this mission completed as soon as you can to unlock Ackbar who will come in very handy for collecting a bunch of minikits during Free Play mode.
Minikit #1 - Free Play Mode
Make your way to the back right where the box with double grapple plugs is.
Use the force at the water's edge to extract the droid.
Bash it open to get the parts for a minikit.
After building a bridge to reunite the temporarily separated group, cross over to find a pool for Ackbar to have splash about in.
When he's done, he'll get you the parts for a minikit.