We always remove the excess/waste vinyl (it's called weeding

) then apply transfer tape, your supplier can cut a log to various widths to help with different sizes of cut vinyl, or they may just sell the width you're after seperately.
The only time we don't weed is if the lettering is small or if the project needs to be a stencil, easier to pull out the letters with the vinyl in place, but transfer tape is still used.