how do i replace the timer nob on a whirlpool awg995 washer dryer?

A repairman came buy to replace the pump on my washer/dryer and when he was here i pointed out that the nob was illegible for the timer, so today i recieved a replacement nob in the mail but with no instructions on how to replace it...

having examined it, it appears to have tabs that lock it into place, but how do I remove the old nob then? do i just pull till it breaks the tabs, dosen't sound like a good idea.