Already play Quaver? This guide will walk you through migrating most of your data to Interlude.
If you encounter any bugs or things that don't look right, feel free to ask in the Discord server.
In Options > Library, there is a tool for linking your existing Quaver Songs library to Interlude.
It will first try to auto detect the folder, but if that doesn't work you can just link by dropping your Quaver 'Songs' folder onto the Interlude window when the menu asks you to.
By linking your libraries instead of fully importing them, audio files and background images are not copied, so the Interlude version of the song library should only be a few MB (saves on drive space if you play both).
There is also an option to automatically import newly added charts whenever Interlude launches.
It may take a few minutes to complete the import, but it will work in the background and you can play what songs have already been imported.
You can also download new osu! Beatmaps or Etterna packs ingame via the Import screen.
There is no automatic conversion process for Quaver skins, but on the Noteskins tab of the Import screen, there is a button to detect and import skins from osu!
The game will prompt you for which keymode to import, and then try its best to convert the skin to a matching Interlude noteskin.
If you don't have an equivalent osu!mania skin, you could try you hand at porting your skin by renaming files manually - see the Noteskins guide.
Alternatively, there are many noteskins available for download from the same screen - If you use a common skin it may already be there!
Under Options > Gameplay > Scroll speed, there is an indicator of what Interlude scroll speed is equal to what Quaver scroll speed.
Once that's set up, I recommend using Practice Mode to adjust your hit position and audio sync to your comfort.