If you are purchasing your vehicle and making payments towards the purchase, then you can select that you own it.

If you are paying monthly payments for the vehicle and have to return it after a certain amount of time (i.e. a lease), then you would select you "lease" the vehicle.

It sounds as though you will one day "own" the vehicle after you are finished paying for it, so I would select "Own".

If you are "buying" your vehicle, the title is in your name so you own it for tax purposes.  You aren't leasing it.  The title may be held by whoever your loan is with and may have a lien entered on the title.  When paid in full that lien will be released (satisfied) and you will get actual possession of your title.