To find it, you'll likely need to:
1. Consult your owner's manual: This is the best place to start. The manual will have a diagram showing the location of all fuses and relays.
2. Look in the fuse box under the dashboard: This is the most common location. The fuse box usually has a cover that can be removed to access the relays and fuses. The flasher relay is often a smaller component, and may be labeled.
3. Look for online forums or repair manuals specific to your 1999 Chevy Cavalier: Searching online for "1999 Chevy Cavalier flasher relay location" might yield images or descriptions from other owners who have located it.
Remember to disconnect the negative battery terminal before working on any electrical components. If you are not comfortable working on car electrical systems, it's always best to take your car to a qualified mechanic.