Back in PlayOnLinux, click on Next...
... and then on Browse:
Select the Safari executable you've just downloaded from your hard drive...
... and click on Next:
The next message tells us to deselect Install Bonjour for Windows and Install Apple Software Update during the Safari setup - please keep this in mind, we'll need it soon:
The Safari installer starts. Click on Next >:
Accept the Safari license:
Now it's time to disable Install Bonjour for Windows as well as the Apple updates. This is important - otherwise Safari might not work as expected on Linux:
Now Safari is being installed:
Click on Finish to leave the installer:
In the next step PlayOnLinux downloads and installs the Adobe Flash player for Safari:
Click on Yes if you want to have a Safari shortcut on your desktop...
... and in the menu:
The Safari installation is complete, you can leave PlayOnLinux now:
Now you can start Safari:
This is how it looks: