How to add the custom theme to SharePoint-site.

Now I learned enough to begin customizations of my SharePoint sites. Unexpectable for me, I found a lot of short tutorials about SharePoint in www.youtube.com
First of all, I found excellent promoting videos for my presentation. Some companies posted case studies about SharePoint as new document management technology.
At my surprise, Coca-Cola has around 1,000 SharePoint sites, using SharePoint Monsanto increased work efficiency by 40%, even non-profit organizations such as
Leukemia & Lymphoid Society implemented SharePoint. Comcast offers SharePoint site as a part of their business internet package.

For now, I found a very good short tutorial to customize a theme on my site. It's really helpful.
Watch the video