I've never setup PPPoE so I don't know the specifics on that. In general, what people (should) do to find out how to do something, is look it up, once they know enough of what is going on. You didn't know about PPPoE before, so that's a reason you would not have known to search it (with other keywords to focus on Linux and not get answers for Windows or BSD for example). Look for descriptions that best match the Linux distribution you have (e.g. Debian? Fedora? Slackware? etc? ), and the version or something close to that.
Here is where you can read what PPPoE is and how it works. This won't solve your problem, but it might provide information to help give you a better idea of what is going on, and perhaps better understand the HOWTOs and other documentation you find. Much of that can be overly technical for you, but parts may help.
But you need to do the google searches for actual setup documentation that match your situation. Or if you want to see if someone here is willing to tell you how (it won't be me), at least tell them more information, like which distribution and version you are using, that it definitely is ethernet.
Another option is to consider buying a wireless router. What most of these routers do is talk whatever protocol the ISP talks (their setup menus may ask you if it is PPPoE or other) and then passes it on as the usual ethernet and wireless communications.
You might also ask your ISP what you need to do to "go wireless".