Lockpick 20 chests.

In order to get this achievement you must lock pick 20 chests.

1. You can only lock pick chests that a coloured red on the map.
2. Find one of these on the map and go to it.
3. Once you get to it, you might have to fight off some guards so be ready.
4. The press B to interact, it will bring up a sort of mini game, once the slider is in the blue area press A and it will open it, you might have to do this multiple times to get it.
5. Repeat this process 20 times and the achievement is yours.

You have to have Apprentice locksmith unlocked to get this achievement.
It really does help if you have the other lock picking skills unlocked as it makes it a whole lot easier.
Stock up on lock picks before you set out, this will save you a journey to the shop as you will need more.

If you need any help feel free to PM me.