Each reply in any forum thread should have a red box-shaped button labeled "ACCEPT AS SOLUTION," including this one. You'll see it in the lower right of each individual post, beneath the REPLY and QUICK REPLY buttons.
We hope this helps!
The "Accept As Solution" option just allows other users who might be browsing through to see which solution worked for you. It's a courtesy to future users, though not a hard requirement. If the button isn't there, don't sweat it. What matters is that your problem was, in fact, solved.
Thanks again for using the Canon forum!