how the heck do you delete things feom your signaturwe!!!!

so ummm im kinda new to forums in general.. and im on tablet if thats worth anything i think things might be different for mobile users

but i got this big fat gif of Konata Izumi from hit slice of life anime Lucky☆Star eating a chocolate cornet and i want to remove it!! but i dunno how!!! SOS!!!!! help!!!!!:'(