Press Alt+F9 on what you want to take a screenshot of. It will now be in your screenshot folder in, which by default isDocuments\Sports Interactive\Football Manager 2011\Screenshots.
To put them in your blog you can either host them on the forum or elsewhere such as photobucket or imageshack. To host them here, while making a blog post click the paper-clip
, click Add Files (top right), click Select Files, select the screenshot(s) and click Open, then click Upload Files. They're now uploaded to the FM-Base servers and you can put them in your post by selecting them from this interface and choosing to Insert Inline.