You can move/copy glTF files into your project's Assets folder, similar to other 3D formats. glTFast will import them to native Unity prefabs and add them to the asset database.
Don't forget to also copy over companion buffer (.bin) and image files! The file names and relative paths cannot be changed, otherwise references may break.
Select a glTF in the Project view to see its import settings and eventual warnings/errors in the Inspector. Expand it in the Project View to see the imported components (Scenes, Meshes, Materials, AnimationClips and Textures).