Do not wet the string. Wetting the string will cause the chalk to cake in the reel and on the string.
Here are some instructions.
First you must fill the chalk reel with chalk.
1. Take the cap off the chalk bottle.
2. Using scissors or snips cut the tip off the cap.
3. Open the slide door on the side of the chalk bottle.
4. Pull out approximately 12' of string.
5. Insert the cut tip of the chalk bottle into the slide door opening and squeeze the chalk bottle. This should force chalk into the reel. Fill it about 1/2 full.
6. Close the slide door and wind in the string. You can then repeat steps 3 and 5 filling the reel with more chalk. Don't fill it completely full. Place the cap back on the chalk bottle.
7. Pull a longer length of string then you'll need for the first marking job 6 - 8 times and rewind to coat the string with chalk.
8. Assuming you have two marks made to strike a line between place the hook on the edge of the board, or on a nail, or have a friend hold it on the mark.
9. You place the reel end of the string on the other mark.
10. Pull the string tight, grasp the string and lift it off the surface about 12 inches and release. The string should snap back to the surface and make a straight line of chalk between the two marks.