Sofia's flat is absolutely wonderful. Great place in the historical center of the city, close to metro, great walks around including walk to seashore, supermarket very close, great comfortable bed, everything clean and nice. And communication with Sofia is easy and fast. (If you miss any detail, most likely you just overlooked it among all the good information she sent you :) )
There are few steps to access the flat, like at most places in Lisbon, but we quite enjoyed walking these. For arrival with suitcase, my best bet would be to go to Baixa station (blue and green lines of metro), walk Rua da Vitória straight end to end and use the free public elevator (works during day only) to the top level. You will also find the supermarket there.
Overall, I can only recommend this. Certainly among the top Airbnb places I visited - and I visited only good ones so far.