Travel to Linz
You have different possibilities:
Linz Airport (LNZ)
This airport is close to the town. Main connections are to Frankfurt, Düsseldorf and Vienna. An airport bus (about EUR 3.-) or taxis (about EUR 30.-) take you to the center.
Vienna Airport (VIE)
There a numerous connection to VIE. Maybe you will find cheaper flights to VIE than to LNZ. Every half an hour there is a very nice train Connection (less than 2 hours) from VIE directly to the center of Linz. The price for a tickst can be seen at www.oebb.at/en/. Cheap rail tickets are indicated as “Sparschiene”.
Salzburg Airport (SZG)
SZG has more connections than LNZ, but you have to organize your travel to Linz by train.
Linz has good train connections to many cities in Europe. Inside Austria there are two companies operating
OEBB www.oebb.at/en/ (national and international) and
Westbahn westbahn.at/en/ (some national connections)
from West or East
Take the A1 motorway and leave at Exit Linz for the A7. Follow the signs to “Center”.
Take the A7 to Linz and leave at exit “Prinz-Eugen-Straße.
Flixbus offers connections to many European cities.