I want to Connect 2 CDJ's to my XDJ-XZ

As Channels 1 & 2 are used by the controller, would I then use channels

3 & 4 for the 2 CDJ's  My question is do I put the CDJ's into  the line input

or do I link them both so I may use them w/ Rekordbox so that I may see 4 CDJ's in the Rekordbox software?