'ls'. The commands are the same as on most any Linux system, so you can just look up Linux terminal commands.

Looks like the account should be removable using 'mc-tool remove MSN', though I may have that wrong. Once the account is removed, the phone should not attempt to connect to it. Note that no specific MSN application was installed in that tutorial - the installed packages just allow the N9's accounts system to connect to MSN, then mc-tool was used to create and enable the account.

Alternatively, to wipe the whole device you can reflash your phone, instructions are stickied on this forum.