1. Extract archive wherever you want
2. Create $HOME/.gaiasky/ (windows) or $HOME/.config/gaiasky (linux, mac)
3. Copy global.properties file to $HOME/.gaiasky/ 
4. Run gaiasky.cmd script (windows)
5. Download base-data a catalog (large?), NBG, SDSS and hi resolution textures with the download manager
6. Start gaiasky, wait until all textures are loaded (some HUUUGE textures in ultra quality)
7. Enjoy ;)