Direct Answer
Transport and Aircraft

Use helicopter transport when it gets friendlies or supplies to the fight faster. Team17 explicitly describes that role; the Supporter Edition also names a Littlebird Taxi cosmetic.
Buying a Vehicle

Open the vehicle vendor, compare the displayed price and availability, then choose a vehicle that supports the immediate objective. The captured roster contains build-specific entries and unlock gates, so check the live menu before relying on a price or availability rule.
Using a Vehicle

The captured in-vehicle UI shows Exit Vehicle and Access Inventory prompts. Use those controls as your first reference in the current build; cargo and seat rules are not published as a permanent specification.
Armor and Artillery
Official copy references heavily armoured tanks and artillery tanks for changing a battlefield approach. Their exact roster, weapons, seats, and current prices are build-sensitive.
FAQ
Can helicopters transport teammates?
Yes. Helicopter transport for friendlies or supplies is explicitly mentioned by Team17.
Is the full vehicle list confirmed?
No. The captured vendor shows its own build’s entries and gates, not a permanent final roster.
Related Guides
Gameplay Beginner Guide Cash & Economy
Sources
Team17 WARDOGS overview
Supporter Edition announcement
Supplied pre-release Vehicle Vendor and vehicle-access captures.