This is a GUI based on the Grive2, a Google Drive clients that syncs all the files in your Google Drive into the current directory.
You need to first install Grive2. For detailed instructions, see http://yourcmc.ru/wiki/Grive2#Installation
git clone https://github.com/yanxi0830/grive-ui.git
cd grive-ui/
make
cd ~/googledrive
~/git/grive-ui/grive-main-bin
Choose the directory you want to sync with your Google Dirve and click Sync. Grive will start downloading files from your Google Drive to your directory.
When the directory is used for the first time, you should click Authenticate to grant permission to Grive to access your Google Drive. A dialog should appear with a URL and prompt. You should go the the link and get an authentication code, and paste it into the prompt.
If the authentication succeeded, Grive will create .grive and .grive_state files in your directory. You can then click Sync to download files from your Google Dirve to your local directory.