Pick a font and design for the alphabet stencils. Compare options at a local craft store or online store. Take into account the size of the letters.
Decide on a design for your stencil project. Stencil letters around the ceiling edge or mid-section of the walls.
Clean and dry walls before starting.
Line up all letters on a straight line by first measuring all the way around the room and drawing a straight line with light pencil that can be erased later. Use a level or measuring tape to draw your guide line. If you don't want the letters in a straight line, consider putting them in a curved pattern that's easier to stencil.
Place the first letter stencil where you want it. Hold it in place with painters tape. Use a stencil paint brush, and paint over the first letter until it is done. Remove the stencil, and repeat the process for each letter.
Add a line under the letters by painting freehand, or use the letters as part of a bigger project or mural on the wall.
Consider covering the finished alphabet with a clear sealer if it is near the bottom of the wall. This protects it from stains, and allows the wall to be washed without affecting the stenciled work.