Spin an album on turntable A and bring up the volume on channel A. The cross fader is all the way to the left. Now, while it's playing through the speaker system to the audience, cue up a track on turntable B through your headphones. Remember, the cross fader is all the way to the left side, but your headphone toggle switch is all the way to the right. Keep in mind that on a turntable, a cue must be back tracked enough from the desired start point so that the DJ device is up to speed by the time it reaches that point after the "on" switch is engaged. Before starting the turntable, using fingers directly on the label of the record, spin the disk back and forth until you've found your beginning note, then you turn the record backwards far enough from that note so that when you hit the "on" switch the record will be spinning at full speed.
Now as your song on table A comes to an end, switch on turntable B while bringing the cross fader to the center and on toward the right as song B begins to play. You can time this so that A jumps into B or a smooth cross fade takes place, much like the lapse dissolve in film where two images linger together before transitioning away from one to the other. Now that you've faded from table A, you can delete that record and cue up another, reversing the process you just completed.
Another good technique of cross fading involves beat matching and takes more and more practice to accomplish. Listen to both the live track and the cue track through your headphones, playing both tracks at speed. By varying the speed of the turntable you can get the best beats to match up. When you've got both thumping together you cross fade and the songs seem to merge. Then you have scratching, and mash ups and all kinds of remixing techniques and devices, but practice the basic things first and you'll be on your way. Improve your ability! Sure, one day you can be a professional DJ player. Learn more about DJ mixing using video tutorials.