Making levels for game

Working on a game for a friends daughter for her 6th birthday. Its a scrolling game where the player will be Snoopy and they'll be flying around on his doghouse collecting Woodstock (Which are flying around the screen) for each level (There will be 4 levels). At the end of each level, the game will have an intermission and show a 10sec video of Snoopy dancing. The background will play the Peanuts theme song. Ive figured out everything except how to make levels for the game. I've tried using a timer but that didn't seem to work very well. Everytime Ive tried to include the block of code I've written the screen doesn't add it and returns back to step one of asking a question on this forum.