The relays are located on the "firewall" in front of the fuel tank under the hood. They are fastened to that firewall and just plug into connectors on the wiring harness. BUT there are often several relays of the same type so you may have to hunt to get the right one. I think the starter relay is supposed to be the most outboard on the right side (driver's perspective) but I have read of cases there the connectors were switched so a different relay relay actually controlled the starter.
Since you have the replacement relay, go ahead and try it. But there are several other possible causes for this no-start problem, such as a dirty/corroded ignition switch or failed battery cables (failed under the insulation where it is not visible). There are MANY discussions of the no-start problem here on this list. I recommend a systematic approach with a schematic and a volt meter. If that sounds foreign, you may want to get help from someone with electrical troubleshooting experience.