I have cracked the screen as it had fallen off my locker but working

The only thing that can really be done is to replace the screen. There are some disassembly guides here: Acer Iconia A1-830 but it doesn't specifically cover the screen and it doesn't look like iFixit has the screen for sale either.

you have be able to buy a screen somewhere on the internet or buy another unit with a good working screen (but other issue like dead system board) and steal the screen from it to put on yours.