MEO fiber does not use PPOE. To connect your own router there’s two options:

* connect your router to the Fiber router (gateway), via bridge mode. (this way you have to use meo router for voip/telephone line and setup meo box). 
* connect your router directly to the ONT (this only applies if your ONT is separated of the router). If you have ONT+router (2 in 1) than you should do the 1st step (connect via bridge mode).

it is explained on the router manual/tut or here https://kbase.pt/fibergateway-meo-configurar-em-modo-bridge/