Several urban trains stop at Frankfurt Airport which offers a convenient alternative to arriving by car.
The airport’s regional train station is served by RMV with direction connections to Frankfurt, Hanau, Aschaffenburg, Mainz, and Wiesbaden. You can use either the trains of the s-bahnlines S8 and S9 or the Regional Express (RE) with the numbers RE59, RE2 and RE3. It’s easy for you to get there from anywhere in the area served by RMV by transferring at any of those places.
The airport's station for short distances is located in the ground floor of the airport below terminal 1. From here you can reach the areas A, B, and C of the arrivals area. Therefore, you want to follow the sings towards Airport City Mall/Regionalbahnhof.
Moreover, you can reach Frankfurt Airport via it's own long-distance train station, which offers many direct connections within Germany and neighboring countries.