The colon should be placed after the word "Ride". Therefore, the sentence should read, "If you are interested in snowboarding, I recommend you watch Let It Ride: The Craig Kelly Story."
A colon may be used between independent clauses when the second sentence explains, illustrates, paraphrases, or expands on the first sentence. It is important to note that a colon usually can only be used after a complete sentence, which eliminates the options "watch" and "snowboarding". However, it is possible to use a colon in a title if the second part emphasizes the first. The title simply could have been "Let it Ride" or "The Craig Kelly Story," using a colon allowed the title to have a creative name related to snowboarding and also states whose story it is. It would not be correct to put the colon after "Kelly" because you could not use the title on either side of the colon by itself.