In a previous post we had a look at doing an adjustment journal with non-wms stock. If you are using advanced warehouse in R3 you can use the mobile device or if you need to make some bulk updates then you can use the adjustment journal but you just need to be aware of how your item is tracked relative to the dimensions needed in the warehouse like location, license plate and inventory status.
Here is a quick walkthrough
AX2012 R3 CU9
Cheers
Lachlan