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 on-going rental. You need not park it at one our pick-up locations.
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.