It depends on the type of DSL, your router will have to support that type/speed. You will also need to know some settings from Frontier, and they may have to add its MAC address to their network. I would ask Frontier and see what they say, if they support customer equipment, and if they have a list of compatible/recommended devices like most Cable companies do.
Many devices today include a modem (DSL or Cable) and a router into one device. You can actually separate it into two devices, depending on your needs. If you just need to improve your Wi-Fi, you can connect a second Wi-Fi router behind the first one. It can operate in router, or Access Point mode.