If you are making a mix with elevator as master, then you move the stick one way and you'll see one of the %-signs flash. Turn the dial to change that number. Move the stick to the other side and the other %-sign will flash. Turn the dial to set that number.

We don't know what you mean by the down/up, left/up stuff. The percentage of mix determines how the slave channel will mix with the master. If the servo moves the wrong way, just rotate the dial until the "+" becomes a "-" or vice-versa.