This is perhaps one of the easiest of the Challenging scenarios. You have two years to accumulate 900 guests.
Start by placing a food stall, drink stall, Information Kiosk, T-shirt Stall, and a Restroom at every corner in the pathways. Improve the Wooden Roller Coaster (add more trains and delete entrance at the bottom), and connect the pathway to other pathways. Put a mechanic set to patrol at the top portion of the Wooden Roller Coaster, and another at the bottom.
Place some trash cans around the park, since it is a pain to try to clean it up - there is a huge amount of pathway, and the trash will be scattered with no focal points, so you'll have to hire a lot of handymen to clean it up. Place First Aid Rooms near the exits of nauseating rides.
After you have bootstrapped the park, you can open it and charge $20 to $30 for the entrance fee. Clear all the scenery in the bottom of the park - you can accumulate thousands of dollars and perhaps build a Corkscrew Roller Coaster.
Basically, once you have the rides running and shops and stalls everywhere, the guests should accumulate themselves without barely any effort. In fact, you may happen to get 900 guests by the end of Year 1. Just build a new ride or two every once in a while and make sure there isn't any litter or vomit, and the scenario will be very easy to complete.