Measure the size of your slide-out and order a slide-out cover set from a slide-out awning manufacturers like Dometic or Carefree of Colorado. Your slide-out awning will typically be a few inches wider than your slide-out on either side.
Install the mounting bracket above the slide-out opening, using the screws provided with your slide-out kit. Use a level to ensure your mounting bracket is level. Install the mounting brackets that go on either side of your slide-out, using the hardware provided. Since each brand of slide-out cover is a bit different, be sure to read and follow the manufacturer's specific instructions for proper placement.
Use a screwdriver to widen the opening at the end of your bracket where your slide-out awning will slide into. Slide the roll of fabric onto the top bracket and center it over the slide-out room.
Slide one of the awning's end caps onto one of the brackets that you mounted onto the slide-out. Screw the end cap to the slide-out cover using the manufacturer's specific method; this typically involves screwing the end cap to the bracket using a pan head cap screw provided with your kit. Once you've screwed one side, slide the other end cap onto the mounting bracket on the other side of your slide out. When that's done, screw the end caps to the mounting brackets.
Remove any safety devices such as metal pins that have held the slide out in place until installation.
Test the awning's position and function by opening your RV slide-out room. If functioning properly, the slide-out should roll out and retract along with your slide-out room.