After you have exposed your stencil and washed off the excess paint according to the manufacturers directions, it's time to start painting! This means you'll need inks or paints suited to your project. Most likely, you'll be using fabric paints which can be purchased at craft stores and on the Internet for fairly cheap if you don't mind buying larger quantities.
Make sure you purchase a squeegee with a rubber blade and a comfortable handle for this part! You can typically find these in home improvement stores and they're not too expensive to buy.
To start, lay your stencil down flat on your piece of cloth, and make sure there are no wrinkles under it. Then, pour a line of ink or paint that spans the whole way across the top of your stencil design, just above it. With the rubber blade of your squeegee, drag the paint down using firm, even pressure. This will transfer your design flawlessly to your fabric!
Make sure you use enough ink or paint that you can coat all of your stencil easily, and go back over it if you notice there are areas that need a second coat. When you are done, remove the stencil carefully, and immediately, and wash the stencil under warm water. This makes sure that you can use it again, and prevents your fabric from drying to the stencil if left there too long.