Need Help How to scale graphics for vans so they print out the correct size

welcome to signs101.
rasterlink has a scaling-up feature but YOU have to be the one to tell it how big it needs to be.
if you don't know how big it needs to be, grab a tape measure and go measure the vehicle/canvas you wish to apply-to.
if you don't have access to the vehicle, then you can buy templates for any particular model from places like provehicleoutlines.
also, if you're unfamiliar with design & rip software..... youtube videos help way more than any instruction that an internet forum could give you.

 

If you're using pre-made vehicle templates, they're almost always in 1:20 scale, but the scale should be noted on them.

I like to work in 1:10 scale on vehicles, so I scale the template by 200% before I start designing, then when it's time to print, we scale the print job to 1000%, which brings it back to 1:1 scale.