Administrator privileges are required to install Dr.Web. After mounting the drive you will see the following window:
Select Dr.Web anti-virus for OS X . 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 OS X will be installed. Enter the administrator password. Then Dr.Web for OS X will be installed automatically. When finished, click Finish. You don’t need to restart your system after installation.