Default keybinds for the seven keys are: ZXC Space ,./
You can change the game to use fullscreen or change the resolution in the JSON file but only after you launched the game for the first time.
Make sure to put .osz files into the input folder before launching to ensure that there are songs in the Songs folder. You can press F6 in the song select to re-extract files that are in the input folder and press F5 to refresh the song list.
Supported 7k .osz files can be found in the mania section of https://osu.ppy.sh/beatmapsets?m=3 or in a beatmap mirror such as https://beatconnect.io in the mania section any non-7k files are attempted to be removed.