How do I fix this

So som context my crust pants are 5 years old and my button just came off I know ew it was gonna come off at some point but idk when I was hoping my button was gonna last till after Friday because I have a show but it came off does anyone have tips on what to do?

So som context my crust pants are 5 years old and my button just came off I know ew it was gonna come off at some point but idk when I was hoping my button was gonna last till after Friday because I have a show but it came off does anyone have tips on what to do?