I also use them for my watch bands.
First of all, you need to determine the finished length of your bracelet. Using a cloth or flexible measuring tape, wrap it loosely around your wrist. If you do not have this type of measuring tape you can always print one out. This is your wrist measurement but you do not want the bracelet to fit too tight so add a little extra to a fit you prefer.
Pick out your beads that will go between the tiles and lay them out to see how many you will need. Most of the tile beads I create have a continuous pattern so I like to keep them in order. If I need to leave any extras out, I will omit them from either end. Make sure the elastic will fit through the holes of the beads you select. I like to use a heavier (1mm) elastic for strength, whenever possible. Cut 2 pieces of elastic measuring the finished length of the bracelet plus 4"- 5" extra to allow for tying.
Thread the elastic through one side going through all of the beads. Tie a square knot.
Check the fit to see if you need to add or take out any beads. If the fit feels good, then tighten the knot. You can add some glue onto the knot for added security if you wish.
To finish off and hide the knot, take one of the end strands and thread it back through the tile bead next to it as shown in the picture below. Pull on the elastic until the knot disappears inside the tile bead. Trim off the ends by lightly tugging on the strand so that when you let go it springs back into the tile.
Repeat the above process for the other side.
Taadaa! Your bracelet is now finished!
To switch to the reverse side, just twist inside out.
And you now have 2 bracelets in one!