Super easy achievement here, load up the second scenario in the beginner career mode category (Creature Awakens). Getting bronze and silver is dead easy - you already have one ride in the park, just find some flat land and drop the 4 other flat rides you start with and connect them all to a path so you can open them. Next, hire the required staff (2 Janitors, 2 Mechanics and 2 Entertainers) - just open up the park management tab and pick them and drop them whereever. You can hire the staff all at once, don't need to complete the objectives in order. Then, for the gold star, run all the marketing campaigns that attract families, put the simulation speed up to its max and sit back and wait. Shouldn't take more than 10 minutes, overall.