What happens when your system memory (256mb) fills up, where do you install software to

but this isnt the question, the question is

In my system memory trying to install scummvm(which i have not successed installing) i made a folder and now i want to delete it but it wont allow me to it saays read-only
this is the directory

how do i remove the folder wich is called lure
home/user/MyDocs/lure

thank you