To use watercolor tube paint squeeze a bit of the paint out on a palette.
Wet the paintbrush and mix a small amount of the pigment from the blob of the paint. Leave most of the blob untouched.
Add more pigment to the water for a darker, more intense color. Add more water to the mixture for a lighter color.
Save the paint on the palette to use the next time. You can even save the mixed color in the center of the palette and reconstitute it with water the next time you paint
Allow the paint to dry on the palette. Make sure to cover it with a plastic bag or tin foil so it does not collect dust.
The next time you use your watercolor tube paints they will be dry. Start by adding a few drops of water to each color that you will use and then paint as you regularly would.