Hello, i just wrote a massive post and cleared it
Do you have a manual? You need an 8mm ring spanner, big bottle dot 4 and a bleeder fron halfords £3-4 ish
1) Remove small rubber hat on 1st calpier, put spanner on and slide the bleeder tube onto bleed screw, push the plastic thing that is supplied on the tube with the bleeder to squeeze over the bleed screw to hold the tube on.
2)Open the resevoir and keep topped up with fresh fluid, keep lid on when squeezing the lever.
3)Gently undo the bleedscrew and start pumping the lever, you will see the old fluid coming out of the tube and into the bleeder pot. Once you see only fresh fluid coming out of pipe and NO air bubbles, close bleed screw gently but so it is closed and start on other caliper.
For rear, do exactly the same but start with the bleed screw nearest wheel hub.
Personally I would strip all 3 calipers and renew pads if needed.
After bleeding, try to leave overnight with cable tie, with handlebars angled so resevoir is higher so air can travel up and escape the lines.