Before fitting the cleat to the shoe, you need to work out where the ball of your foot is. If you put the shoe on, and stick some tape on the side, you can locate it and make a mark without ruining your new shoes.
Before fitting the cleat, put some grease or thread lock (preferably) onto the thread of the cleat bolt to stop it seizing in place. Loosely fit the cleats to the shoes – position the cleat so it’s under the ball of your foot according to the mark you made.
Pedals come with matching cleats, which will fit all mountain bike shoes:BikeRadar
The angle of the cleat should match the natural standing position of your foot – to get an idea of this, stand naturally and assume a riding position – if your feet point out you should set the cleat position to match. You don’t need to be too extreme with the angle so if you’re unsure, set them straight and you can tweak them later.
Tighten the bolts one by one – when the first starts to feel tight, stop turning it and tighten the other. You will need to tighten as a pair – so alternate between bolts until they are firm.
Put on the shoes and swing a leg over the bike and clip your foot into the pedal. While leaning against a wall or solid object, clip the other foot into the pedal. Give the cranks a few backwards turns to check the cleat position is still comfortable and that your shoes aren’t rubbing the frame or cranks – if so you’ll need to repeat the previous step and readjust accordingly.
Before you take the bike for a ride, practise clipping in and out of the pedals. Twisting your heel out is the best way to release them.