From Twitter for iOS or Android:
Go to your Settings (from an iOS device, tap the Me tab and then the gear icon ; from an Android device, tap the overflow icon ).
Select the account with the block list you want to view.
Tap on Blocked accounts.
You can unblock users by clicking the red unblock icon or visit their profile by tapping on their profile photo.
If you previously imported a list of blocked accounts, you’ll see the option to tap All or Imported blocked accounts.