Prepare the canvas if desired using acrylic paint - you can also leave the canvas white. Let dry.
Punch out shapes from the cards. For a 2" punch, you'll want 80 circles (8" x 10").
Place Mod Podge on the back of the circles and then down on the canvas. Start at the top left and place the circles down. Continue moving across the canvas adding cards and Mod Podge until it's covered. Let dry.
Apply two more coats of Mod Podge on top, letting dry 20 minutes between coats.
Let dry completely before hanging on the wall.
Notes
Select a canvas to fit the number of cards you have - if you use a 1" or 2" punch, it won't matter what size your canvas is as long as the measurements are even in terms of inches (16" vs. 16.25" for example).