Administrator privileges are required to install Dr.Web. After mounting the drive you will see the following window:
Select Dr.Web anti-virus for macOS. Read the Installation Wizard's welcome and click Continue. To continue the installation, read the License Agreement and accept its terms. After that select the disk onto which Dr.Web for macOS will be installed. Enter the administrator password. Then Dr.Web for macOS will be installed automatically. When finished, click Finish. You don’t need to restart your system after installation.