Thank you for using answers.slingbox.com! There is not much to be done when installing the SlingPlayer plug-in. All you need to do is go to newwatch.slingbox.com. It will prompt you to select your country/language, then login. After this it will prompt you to install the plug-in. You will just need to go through the installation. After the installation is complete, all you have to do is go back to newwatch.slingbox.com and you will be able to connect to your Slingbox.
Just for a tip, I would recommend using a 32 bit browser when installing the plug-in. If you run into any issues when doing this, you can also contact technical support and a representative would be more than happy to walk you through the installation.
Below is a link from support.slingbox.com that explains how you can contact us:
Have a great day!
The Sling Moderation Team