Hopefully your solenoid will have two wires on it + & -, if so its easy.
fit an in line fuse holder to your battery positive terminal, run a wire off the fuse holder and into the car, (through a grommet) and then up to your chosen switch location, (somewhere out of the way). connect the wire to one side of the switch, from the other side of the switch, run the wire back to the solenoid and connect it to it's positive side. the other side then is connected to earth, and that's all there is.
Now when you put roughly a 20A fuse in, power will be supplied up to the switch. pressing the button will supply power to the solenoid and throw the boot release, if it doesn't it will go bang so make sure you actually understand all this and wire it correctly. It's dead easy if you know, confusing if you don't. "DON'T TAKE A POWER FEED FROM UNDER THE DASH, IT'S MORE CONVEINIENT BUT A SOLENOID CAN DRAW A LOT OF POWER, AND IF YOU HOOK INTO THE WRONG CIRCUIT IT WILL TOAST YOUR CAR ! YOU HAVE BEEN WARNED" !