If you are new to the Apple OSX or Mac platform and are a little lost as to how to do something, please refer to the excellent Mac basics guide on Apple's web site. It will teach you the basics on how to use the Mac and help you if you have recently migrated from Windows.
All videos should PLAY (stream) without issues on any Mac, but do make sure your browser (Safari, etc) is up-to date.
Now, when it comes to playing DOWNLOADED videos, it gets a little trickier. For downloaded videos, Mac will play all MP4 videos (the movie's file extension ends in .mp4) without problems in Quicktime, which is Mac's default media player. However, some older movies that are encoded as .wmv (Windows Media Video) need either a plugin for Quicktime, or a different player in order to work.
Again, Windows Media Video (.wmv) movie files do not natively play on the Mac, however, with a small additional bit of software they will run almost seamlessly. You'll need a plugin called Flip4Mac to make it work. This used to be free. However, at the time of this writing, the company that makes this plugin appears to have started to charge about ten dollars for it. Go to the Flip4Mac plugin website and download the player for your your Mac's OS. Once it is installed, you'll need to shut down and restart the Quicktime player and you will be able to play WMV videos within Quicktime.
A FREE alternative is the excellent VideoLAN (VLC) player. It can play pretty much all file types, including .wmv. You can download the VLC Player here.
If you continue to have problems with members area photos or videos on your Mac please fill out the form on the contact us page. Please note that we are not able to troubleshoot any Mac issues unless they directly relate to the website you are a member of and while we will do our best to assist you, computer problems specific to your situation may not be within the scope of our experience. We are here to provide assistance with the website you have subscribed to, not general Mac help.