With scissors make one cut in the middle on the top of your cardboard, and make several cuts on the bottom of your board. The amount of cuts across the bottom of your board needs to be the amount of strings you will have in your bracelet, or more.
For my bracelet, I cut a ~6ft length of thread from each of my three colors. I like to error on the side of way too much thread than too little (I've been on the too little side too many times...). Once you have your three lengths of thread, fold them to find the center.
Now you're going to grab the center of your three strings you just found and make a knot, leaving a loop. Pull tight.
Using the center cut on the top of your cardboard, place the loop and knot behind your cardboard, with the strings coming out in the front. Arrange your strings in the order that you'd like your colors to appear in your bracelet. Separate out the strings, and put each string through a cut on the bottom of your board, make sure they are pulled snug. We're going to start the bracelet with the string to the far left.
Pull the string to the farthest left (green) out of the bottom cut in the cardboard, and make what appears like the number "4" with your number 1 string in the picture.
Fold your farthest left string back under your number 1 string, and pull the end up through the loop created.
With the same green string, make a number "4" again, and this time make your loop around the 2nd string.
Continue the process until you have made a knot on your 3rd, 4th and 5th string as well.
Your first row on your bracelet will appear like this. Now pull the green string you just finished using down through a cut to the farthest right bottom of your cardboard.
You'll now continue the process with the string that is now to the furthest left following steps 5-8. This is the process you will continue until you get to your desired length.
When you get to where you have no more cuts to the right of your board, shift all of your strings back to the left of your board and continue on.
Once you finish your bracelet and remove your strings from the bottom, it will curl up on itself. If you run your bracelet under water and stretch it out, it will help straighten it out. I've even wrapped bracelets in paper towels and placed heavy books on top of them to dry. Whatever you gotta do ;)
Once your bracelet is dry and flat, tie a knot at the end so that the bracelet will not unravel.
To tie your new bracelet on your wrist, you will basically make a bow like tying your shoestrings. This is if you want to be able to remove your bracelet. If you want to permanently leave your bracelet on, just make a knot and I would suggest putting a dab of clear fingernail polish on the knot to keep it from untying.
Leave me feedback if any part of this tutorial isn't clear enough! Hope you enjoy :)