Audio tracks into midi project and vice versa

Can anyone help? - I have been using Cubase SX for ages and have now started using Cubase 5 - Can anyone tell me how to Insert an audio track into a midi project and vice versa - a somewhat simple porcedure seems to be overly comlicated - I’m a musician not a producer so a step by step-easy-to-follow-guide would be appreciated! Eeen on Youtube but full of geeks talking nonsense. Thanks

What do You mean about “a MIDI project”?
Cubase projects always can include MIDI- and Audiotracks.
So, Import/ Audiotrack - that’s it.