Hi Archery - sorry the forum volunteers hear the same questions over and over again and they forget newbies need a little extra care - but hey - it's ok.
Changing colors is a little harder to learn than just pushing a button. Once you prepare your print for printing you need to save the file to a memory card. Then you take that file and open it up in an editor - I use Notepad ++, it's free and does a good job. Once it's open you need to determine what layer you want to make the change on. I do that with the preview screen and slide to the spot I want. Now open up the file you just saved to the memory card. Then in the editor, you search that file for that layer with a search of - for example, you wanted to change at layer 40 so you search for "Layer 42" finding that line in the code. Hit the space bar and then past this next lines of code into the editor at that point:
G91 ; set relative positioning
G0 Z60 ; raise Z (drop bed)
G90 ; set absolute positioning
M84 S0 ; disable idle timeout
M25 ; Pause SD Print
G92 E0 ; zero extruder
Now hit save on the file and put the memory card into the printer.
Now with the printer connected to your computer still go to the "machine control panel" you're going to want to "Print from SD card" find your new file and start the print.
When the printer comes to the layer you want your change to take place it will stop and lower the bed a bit. Now is the tricky part. From the jog command in the machine panel press Retract 100 twice to kick out your filament.
Ready your next color and insert it into the extruder - now press extruder 100 twice and be ready to gather the filament as it comes from the nozzle. I use a small pair of needle-nose pliers so it doesn't stick to my existing print. Don't move the print head or you'll screw up your print. For every retract command you must have the same number of extrude commands, no more and no less.
Back to your machine panel, press pause SD print once and it will change to resume sd print, so press resume.
If you followed this you'll jump for joy as your print starts printing again and you have changed colors.
If you search some more in the forum you will find very similar instructions Go ahead and play with it with a simple print. I just finished a print with 7 color changes and it turned out great.
Happy Trails - Papa