You can open or close a door for 1 AP. If you have the key to the door, you can use it to lock or unlock the door as part of the same action. 

If you don't have the key and need to lockpick, you can do so with disadvantage or spend a second AP to roll normally. As part of the lockpicking action, you can then open the door.

If you wish to slam through the door as part of your movement, you still need to spend the 1 AP for the door, but can continue your movement afterwards. If the door is locked, roll a Check for Body STR.
Example: Spend 2 AP to run 3 sq toward the door, burst through it, and then run an additional 3 sq.