When You get the brushes, it will be very self evident what they are and where they go. Unsolder from capacitor and motor lead first.

You can use your fingernail or small flat blade to pry them out from the can cap; starting at the bottom; gently pry upwards and it will pretty much fall out from there. Then, insert the new ones top first, then it will 'snap' in at the bottom of the upper can cap.

Use paste flux on the old joint and it will melt much faster and won't cook the solder joint too long as You will melt the plastic cap. You want to be on and off as fast as possible. Remember the wiring configuration red/black. Do it one at a time or mark a dash on the can for the neg. or something.