Good morning,
We have started using the locations but it generated a huge problem with the rest of the supply chain in Dynamics.
All of a sudden, the program was asking us to input location at every level: purchase orders, invoices, production orders,…Then there was a conflict between the documents set up before the “location” change and after.
We quickly decided to abandon the whole idea and went back to the previous setup in “dimension group” (without location).
That said, I am going to give you a summary of the whole story 
There are 2 ways to use location, the first one is to change the dimension group in the item card, the second one is to manually input the location in the item card. What is the difference? It is in the traceability.
1/ Dimension group should be used only if the data (could be warehouse, batch number, location or serial number) is crucial for the informations’ management. For example, for garanty and accounting reasons, your finished item needs a serie number that cannot be repeated. In that case, you configure your dimension group with “serial Nos” in the main table form of the dimension group.
2/Manual input of the location (rack and shelf fields) in the item card without configuration in the dimention group, will limit the use but the dead ache as well 
The location field will not be active in any other window than in the item card but you can still use it to facilitate your stocktaking: Just “sort ascending” in the field “rack” and then transfert the file in a excell sheet.
In general, be careful about the explainations your consultant is giving you. Those guys have no idea what a supply chain is and what it implies. There can be months between the time a purchase order is created, the part is received, invoiced and then used in production. Making a change in the core definition of an item means that all the documents where the item is used will need to be updated manually.
Have a nice day and may the force be with you 