The question is quite vague to be honest, what do you mean by "remix" in Cubase?
Although i am not well versed in remixing other tunes (not somethign i do) i would imagine remixing a tune is just like creating one although you all ready have the parts (be it midi or audio).
I assume you have got your hands on a remix pack from some site somewhere and if so its simply a case of importing the parts and manipulating them as you see fit, almost like working with loops.
If, however, you are talking about the "remix" function in Cubase where you have your own track crated then you select certain sections of the track to create a "remix" of your track then this is how thats done....
1. Create an arranger track (done as you would create any other track )
2.On the arranger track use the pencil tool to draw in the sections that you wish to use in the
re-arranging of your track (so for instance draw a "block" where you would like the intro to be - these are called parts)
3. Continue to create parts related to the sections of the track you have. They will be lettered from A upwards.
4. once you have done this for your complete track you need to create an "arranger chain"- Click the e button in the inspector for the arranger track - the arranger editor should appear.
5. On the right hand side you will see the arranger parts you created in the main window 0 you can rename them here
6. The section at the left handside is the arranger chain, drag the parts from the right hand side to make any arrangement of these parts you like. This is where you also tell cubase how many times to repeat each part.
7. To play the arrangement make sure "arranger mode" is selected in the tool bar on the arrangement window. Press play. Cubase will then play the track as you arranged in the arrangement window.
Hope this helps you out mate,
Any problems let me know,