From the main train station downtown it is around 10 euro cab /taxi ride, depending on traffic.
You might like to start by looking at the Tripadvisor page called Porto: Public Transportation. I cannot post the link as Tripadvisor doesn't allow me to. Try searching using tripadvisor Porto Portugal Public.Transportation.
Metro station Casa da Musica is the nearest station to the hotel but, while walkable, it is a bit far with a heavy case.
The bus network passes closer to the hotel. For a journey planner (making sure you have selected the English text version). Again, try searching using stcp en itinerarium
Hope this helps.
From Casa Musica subway. Walk toward the spectacular Peninsula Memorial, straight through the park and keep going the hotel is on the left just after the mercado.
From Casa da Musica there is some walking to do if you don;t have much luggage.
Nice easy walk from station head towards the big roundabout with the lion and eagle statue. At roundabout go to the left and head towards Praca Bom Sucesso. Walk down this road and the Fenix is just past the market/shopping centre. If unsure try Google maps on your phone.. ENJOY !.
Get an answer from HF Fenix Porto staff and past guests.