How do i clean my washing machine, (i dont mind what way) but its looking rather gross, ive had it for a few years.. (ok 6..) and have never cleaned the inside

suggestions?

Its an older one (it was new in the box when we got it) like has the dial thing no buttons.. it has one of those things in the middle that you put your fabric softner in.. i had a peek and it looks nasty

please dont judge me.. ha