Download & Launch the across Installer: Download the zipped across installer file and unzip it. You will see two directories differentiated by macOS version. Go into one of them depending on your macOS version and launch the across Installer in there.
Agree & Confirm: Read carefully the across EULA on the installer's License Agreement phase and if you agree to all of its terms, click [Agree]. When the installer requests your password, enter your password.
Get Started: Upon completion, you can see that across is running in the Dock. The across Client mode is the initial operation mode. You can switch to the across Server mode from the Dock icon menu.
macOS 10.14 and later: macOS added a new security mechanism to prevent an app from controlling another app without the user's consent. That is, you are able to register an app explicitly as an exception in the allowed list from [System Preferences]. To do this, please follow the steps below: