I've done this many times now; a few in Crestview at our first house and more recently in the house we're renting (17 blinds needed to be put up!).
This house is a little older and has somewhat odd windows, but the basic procedure for putting your own blinds in is the same.
Here's the original wood blind that let in too much light.
I took the old blinds off its hooks and prepared the window for the new vinyl blinds.
I held the blinds unit up in the window frame to get an idea of how it fit.
I dumped the packet of installation hardware into a bin so that I didn't lose anything. This includes the mounting screws, mounting brackets, valance clips, and center support bracket.
I then held the mounting brackets up against the wall and marked the hole positions with a pencil. I drilled a starter hole and then screwed the brackets in place.
A couple of my windows were too narrow to allow the blinds unit to fit, so I sawed a bit of the end off. It works fine, but hopefully it'll be unnecessary for your mounting situation.
The blinds can be set into the brackets at this point so that you can measure where to put the center support bracket. I make marks around the center support bracket and then screw it in. I usually leave it a little loose so that it has some give to allow fitting.
Once the center support bracket is clipped in you can slide the bracket covers in place on each side.
Put the valance cover clips on by sliding them over the top.