If you're playing as a thief, or simply want to uncover every possible item you can, you'll want to know how to lockpick. Here's some handy information from the game's support site.
Elder Scrolls Online Lockpicking Guide: How to pick locks
The first thing to remember is that lockpicks are consumable items. That means you'll need to have some in your inventory to be able to access the lockpicking system.
Here are some handy hints straight from the devs:
- PC/Mac players should position the lockpick over a tumbler and then click and hold one of the mouse buttons to move it
- Xbox One players can navigate over a tumbler using [Left Stick] and hold [RT] to move it.
- PlayStation 4 players can navigate over a tumbler using [Left Stick] and hold [R2] to move it.
- Players should then release the tumbler when it reaches the right position in the lock.
The game will give visual and audio hints when you're close, and there's also a time limit for a lock. There's a handy section in this video at 1 minute and 10 seconds.