For fabric, most just glue it on. Get some fabric glue at your local fabric supply store. Its usually white glue that hardens clear. Spread it lightly, and use a toothpic to spread it into the corners and to the edge of the leather, so that the fabric totally sticks.
Use masking tape to tape up a section of the shoe, then cut it out with an exacto knife. Place your tape stencil on the fabric and cut around it. Then peel off tape, and glue onto shoe! shaboom! Jsut watch out that the threads dont stick to the tape and frey your fabric once you take off the stencil.
If youre wanting to paint any areas, use Angelus leather paints. Throw down some acetone first to get rid of the clear coat on the leather, then paint, and it will stick.
But just fabric is pretty simple enough. G'luck