There are two train stations at FRA airport, one for long-distance connections (Flughafen Fernbahnhof) and one for regional ones (Flughafen Regionalbahnhof). The latter is underground. To get to the city centre, take an S-Bahn (suburban train) from Regionalbahnhof. Either take an S8 (direction: Offenbach Ost) or an S9 (direction: Hanau Bhf). The ride is about 15 minutes.
The two main stops in the inner city are Konstablerwache and Hauptwache. Both stops have several U-Bahn (tube) and S-Bahn routes. There are also several bus and tram lines. From Konstablerwache and Hauptwache, it's easy to get to both the pre-party venue as well as the festival venue.
Side note: Don't get confused when you read "Frankfurt/Main" - "Main" does not refer to the main station, but to the river Main (it distinguishes "our" Frankfurt from another German city by that name). The main station in Frankfurt is called "Hauptbahnhof".
Just like each year, the pre-party is held at the office of UFD host, byte5. It is situated at Hanauer Landstraße 114, on the fifth floor of East 114.
With a bit of luck you'll find a parking spot on the surrounding streets. Otherwise there's also paid parking on Lindleystraße or at Weisbachstraße car park.
In Frankfurt and its surrounding area, the public transport company is called RMV. Buy your ticket at one of the Umbraco-coloured ticket machines at the stations. Keep in mind that even though using debit and credit cards is not uncommon, in Germany cash in king. You can check your connection either on the RMV website or in the RMV app.
The closest train station is Ostbahnhof. You can get to the office easily from the centre of town (e.g. Hauptwache or Konstablerwache) taking underground line U6 (direction of Ostbahnhof). Coming from Frankfurt main station, you can also take tram line 11 (direction of Schießhüttenstraße) to Ostbahnhof/Honsellstraße. This might take a bit longer, but you go through the beautiful city centre of Frankfurt on your ride to Ostbahnhof.
This year's venue, Westendcarree, is situated in Frankfurt's Westend, more precisely at Gervinusstraße 17. How to get there best, you wonder?
A thing which applies to most city centres of metropolises around this world also applies to Frankfurt: You best don't take your car to go around the city. Frankfurt has excellent public transport. Many hotels offer good deals when it comes to leaving your car at the hotel car park. To everyone who wants to use their car nonetheless, we recommend Turmcenter multistorey car park on Querstraße 7-9.
To the festival venue on Gervinusstraße 15-17, you can either get by foot. Or you start your short trip close to the byte5 office, taking underground line U6 (direction of Heerstraße) and getting off at Hauptwache. There you change to underground lines 1, 2, 3 or 8 and get off at Grüneburgweg. It's just a few metres from there.