How to get vehicle make and models into the drop down list

When adding a new stock unit in, usually you would select the make and model details from a drop down list. However if the option you need isn't in the list, type in the make or model you require, and once you have saved the stock, the new data will be added into the drop down list for future uses.

Ensure you have the correct spelling, as you won't be able to remove them from the list once saved