To find it, you'll need to:
1. Consult a Repair Manual: A Haynes or Chilton repair manual specific to a 1995 Buick Century will have a diagram showing the location of all relays and fuses. This is the most reliable method.
2. Check the Underhood Fuse Box: Open the hood and locate the fuse box (often a black plastic box). Many relays are housed here. Look for a relay that's labeled "horn" or has a horn symbol. The relay itself may be a slightly larger square or rectangular component, usually with multiple connectors.
3. Check the Interior Fuse Box (under the dash): Some vehicles place relays inside the passenger compartment fuse box, usually under the dashboard. Again, look for a label indicating a horn relay or check a fuse box diagram (if one is present on the fuse box cover).
Important Note: Before attempting to find or replace the relay, disconnect the negative battery terminal to prevent electrical shorts. Also, if you're not comfortable working with car electrical systems, it's always best to take your vehicle to a qualified mechanic.