I presume you have Verizon (FiOS) for your service provider, as they use Actiontec routers. Another router (such as an Airport Time Capsule) can be connected to your Actiontec router, but you cannot substitute another router in place of your Actiontec router.
I recommend turning off WiFi on your Actiontec router, as it has known security issues which enable it to be easily hacked into. For example, WEP cannot be disabled. Your ATC can be used as a WiFi "access point" instead, providing superior security and speed.
To know whether you are connected to your ATC, you could try unplugging it to see if you still have access through your Actiontec.
To configure your Actiontec and ATC together, as I've described, is too complex to explain here, as you seem to be a novice user based upon your past questions. You can be forgiven for not knowing the differences between modems, routers, gateways, LANs, WANs, etc. Such things are complicated, and weren't designed to be user-friendly.