The closest airport to Liptovský Mikuláš is in Bratislava, and is named after Milana Rastislava Štefánika, also BTS, Bratislava-Ivanka (letisko Milana Rastislava Štefánika). It is the largest airport in the country. It is located near the capital, in the village of Ivanka.
The closest airports to Liptovský Mikuláš are in Poprad and Žilina, but most tourists prefer to travel from Bratislava.
You can see a map of the airport here, and from there you can get to Liptovský Mikuláš by bus, train, cab or car. It is better to check all the details of the schedule on the spot in each case, they change quite often.
The Bratislava Airport website is there.
