although i don't have official documentation with me but i'll definitely guide you how can you change your without location controlled warehouse to location control warehouse ,Please find the below steps to follow in LN,
1.Start the Change Location System by Warehouse (whwmd3205m000) session.
2.Select the warehouse to be made location controlled.
3.Select the items to be made location controlled or copied to the Assign Locations (whwmd3105m000) session.(This is because you cannot assign non-location controlled items to a location)
4.If required, enter a receipt, inspection, reject, or staging location in the location fields.
5.select Simulate for trial run.
6.To actually copy the items to the Assign Locations (whwmd3105m000) session or make items location controlled, select Update.
7.Click Get Stockpoints copy the items to the Assign Locations (whwmd3105m000) session.
8.Start the Assign Locations (whwmd3105m000) session.
9.For each item, in the New Location field, enter a new location as required. The location entered in this field overwrites the location present in the Proposed Location field when you actualize the location and inventory information.
If you want to divide the inventory of a particular item over more than one location, from the appropriate menu, select Split and in the new line that appears, enter a location and the quantity to be stored in the location.