To remove the glazing bead –
Start with the pieces that are running horizontal (top and bottom of the window).
Place a putty knife (or some kind of blade) between the glazing bead and the frame (see below photo), and then carefully separate the bead from the channel.
Once enough is separated, you should be able to just grab it with your fingers and pull it out.
Repeat same process with the pieces that are running vertical (sides of windows).
To re-install the glazing bead –
Start with the pieces that are running vertical (sides of the window). These will need to have straight cuts on the ends.
Slide glazing bead into place starting at the top and then push/snap into place working down the window.
Move onto to the pieces that run horizontal (top and bottom of window), these pieces will have mitered ends.
Slide glazing bead into place starting on one side, and then push/snap into place working to the other side.