Vilnius Airport is Lithuania’s primary international airport, about 7 kilometres from the city centre. (about 20 minutes travel time by car)
Also, you can reach Vilnius by coach. Available options:

Lux Express: Tallinn – Riga – Vilnius – Warsaw
Eurolines: Gdansk – Vilnius, Warsaw – Vilnius
Ecolines: Berlin – Vilnius

You can reach the city in 20 minutes by either bus or taxi. It is entirely unproblematic. The airport has direct flights to major cities in Europe; Scandinavia is within very easy reach. The conference website will provide delegates with all necessary links for transportation and ticket purchasing.