I experienced a fairly carefree process in downloading the app, registering my credit card, then renting and returning my bike.
The next bike app is 24 MB, so you may want to download it in advance and complete your registration. They will charge $1 to your credit card which is later refunded.
Once you enter the bike ID you wish to rent on your app, a code is texted to your? phone that you can use to release the bike.
One beauty of the process is that you can return the bike to any of 50 locations. There's an app feature that helps you locate the nearest drop-off.
The app is clunky, at least in it's Android version, but it does make a fairly complicated process quite manageble.
The seats on the bikes are as adjustable, and the bikes are much easier to ride than I expected.