When prompted for a part number in the Part Master Screen, you can enter either the primary part number or the cross-reference number (vendor's part number). If you're not sure of either, press F1 to access a parts lookup list or F2 to access a lookup list by vendor cross-reference numbers.
When accessing the parts lookup list by pressing F1, you can highlight a part and then click the "Vendor" toolbar button. This will display all vendor cross-references for the part. There is also a checkbox which allows you to display the quantity on-hand for each part (using this option will increase the time required to display the list of parts).
When prompted for a starting and ending part number range, press F2 when in the Ending Part Number field to use the same part number from the Starting Part Number field. This saves you from having to reenter the part number.