Standard installation
Classic installation process for standard users, through the stable channel of QGIS plugins.
Check requirements
In QGIS, check network settings (proxy...) opening menu Settings > Options...:
Install the extension
Open the plugin manager, search for Isogeo and clic on "Install plugin":
Connect the plugin to Isogeo
When you launch the plugin for the very first time or clicking on the button to change authentication in the settings tab), the authentication form is displayed.
Just upload the credentials file client_secrets.json
you must have received by email from Isogeo.
If you have an Isogeo account (means that you can log in here), you can check the I've got edition rights on app.isogeo.com
option.
Et voilà ! Enjoy!