During your rental period, you can park, lock and unlock your bike (preferably at a bike rack), as many times as you want. That bike can only be used by you and won't be assigned to anyone else during your ongoing rental. You do not need to park it at one our pick-up locations if you are still renting it.
Whenever you want to take a break, just tap Lock in the app and push down the lock handle to close it. Then use the app again to unlock the bike when you're ready to roll.