The easiest and cheapest option it to take a local train ("Schnellbahn"), which goes directly from "Flughafen Wien" to "Praterstern". I do not recommend to take the "City Airport Train / CAT", because it is more expensive and you have to change trains in "Wien Mitte".
Take a "S7" or "REX7" from "Flughafen Wien" to "Wien Praterstern". A single ticket is 5.20⬠and the journey takes 27 minutes. This train runs between 4:30 and ~1:00, so unless you have a very late / early flight it's the best option. There are two to three trains an hour.
You can get the ticket at tickets machines in the airport itself (where there are often queues) or before taking the last escalator down to the platform (less crowded usually)
https://fahrplan.oebb.at/
That's the green branded "fast train" going between airport and "Wien Mitte". It takes 16 minutes, but you will have to change in "Wien Mitte" to take another local train or tram to get to Praterstern, so you will definitely lose the time benefit. It costs 14.90⬠for a single trip, and you will have to get another ticket to get to Praterstern, which costs another 3.2â¬
https://www.cityairporttrain.com/en/
Makes even less sense than CAT
https://www.viennaairportbus.com/
Taxis of course are available. Here is one well-known taxi company offering a 42⬠service in one direction:
https://www.taxi40100.at/flughafen/zum-flughafen/