During gameplay, press "P + F2" on your keyboard at the same time.
This will bring up a command console at the bottom of the screen.

Then, copy one line of the following codes at a time into the console and press the Enter.
Each time you do this, you'll receive one of the DLC items.
There are 12 outfits in total, so you'll need to repeat the process 12 times using all 12 lines below:

GetProps,1341,1
GetProps,1342,1
GetProps,1343,1
GetProps,1344,1
GetProps,1345,1
GetProps,1346,1
GetProps,1347,1
GetProps,1348,1
GetProps,1349,1
GetProps,1350,1
GetProps,1351,1
GetProps,1352,1

Be sure not to try any other numeric IDs, as doing so may cause the game to crash or corrupt your save data.