Measure the canvas. Write down the length, width and depth. The depth is how thick the canvas is.
Buy a frame that corresponds to the measurements in Step 1. Many canvases have a generic depth measurement, so be aware that your canvas may not fit if you do not check the depth.
Measure the inner lip of the frame.
Using the measurement in Step 3, purchase a mat and a pane of glass.
Clean the glass.
Place the pane of glass in the frame.
Place the mat on top of the glass.
Place the canvas on top of the mat and secure it with canvas clips or framing clips.