You could also use set of queries.
Let's assume that you have a spreadsheet with Item Lookup Codes and their corresponding Bin Locations in columns A & B.
Enter the following formula in column C: =CONCATENATE("UPDATE Item SET BinLocation = '",TEXT(B1,0),"' WHERE ItemLookupCode = '",TEXT(A1,0),"'")
The result will be a query that reads: UPDATE Item SET BinLocation = 'B1' WHERE ItemLookupCode = 'A1'
If you fill column C with this formula, you'll end up with a long list of queries, each assigning a Bin Location to a specific Item Lookup Code. Just copy the list into a new query window and go for it.
I'd recommend doing this when the store is closed. I'd strongly urge you to backup your database prior to running this query. If it screws up your database, you can restore easily enough.
You'll need a precise match for the Item Lookup Codes from the Spreadsheet in your RMS database. It might be best to run a query like SELECT * FROM Item, export the query, open it with Excel, delete all of the columns except Item Lookup Code and enter your Bin Locations on that spreadsheet. If you already have the bin locations entered and don't want to re-enter, you could use the VLOOKUP function in Excel to find matching data on your existing table.
OTOH, I do also have the EMS Import/Export bundle Rob recommended.
Tom