FBX/OBJ export is available upon request, as it's an experimental feature right now. Please send us a message through chat so we can give you access for 1 month.
Once you have access, to export, just click on Export (next to Publish in your dashboard), and select FBX or OBJ as the target platform:
Then click Export.
A link to download your OBJ/FBX file will appear under Published Versions. Just click the link to download the file. You can also share the link with other people if you would like to share your file with them.