cant remove files in step 3 of removal of flash player

So I have followed the steps to uninstall about 100 times now, that dam pop up box keeps covering up programs I am using & I keep been told I haven't uninstalled it correctly
followed all steps to step 3 when I try to delete the files it says: you require permission from trustinstaller to make changes to this program!
how can i remove these files or stop the pop up box, i have to move my pages to the side of the pop up just save or complete tasks so i can restart my laptop to remove the pop up 😞