I fucked up my amp, how do I put this back in place? It is a

>>274656
Post a pic of your actual amp and knob. If the knob came off like in the picture, then you can just put it back on. Its not broken. Its just a plastic cover for the potentiometer

what >>274721 said
if the plastic cover broke then just buy a new plastic cover, ebay has lots of them
>http://www.ebay.com/sch/Potentiometer-Knobs/58163/bn_7684862/i.html
if your pot metal knob broke (how do you even?) then you need a new pot (checks its specs [ohms, linear or log, size, etc...] and replace)
gl