To get from Lisbon airport to the city center is straightforward. There are several options:
Car Hire at Lisbon Airport
If you plan to do a lot of driving on your Portugal holiday, car hire at Lisbon airport is a good choice. There are car hire desks in the arrivals hall of the Lisbon airport, and many international and local car hire companies operate from there.
Taxis from Lisbon Airport to the City Center
The fastest way to get from Lisbon airport to the city center is by taxi. You can read more about taking taxis from the airport to the city here.
Buses from Lisbon Airport to the City Center
You can take city buses or the AeroBus 91 or Aeroshuttle 96 to get from Lisbon airport to the city center. City buses are cheaper but slower, while shuttles are faster but slightly more expensive. You can learn more here.