You can follow these steps to install Astrill VPN on macOS:
1. Download the macOS Client setup installer from the Astrill VPN Downloads website.
2. Double-click the astrill-setup-mac.dmg file that was downloaded.
3. Using Mac OS 10.8 or later, you can choose Open by performing a Ctrl+click on the file icon.
4. Install the Astrill VPN app by following the instructions.
5. After installation, double click on app to start the application.
6. Open your account and log in.
7. You ought to be connected in Openweb mode automatically.
8. Use the menu's drop-down list to choose a server location.
9. Select Check my IP after clicking the Astrill button to verify your connection.