Please take the following steps:
1. Edit a page
2. Add a Blog Posts control that located in the Blogs group of the toolbox
3. Edit the Blog Posts control
4. Click on the "Settings (optional)" link in the Basic tab
5. In the "Blog posts settings" section select "Summary" radio button and click on the "Set summary" link
6. Set value in the field "Display the first ..... words of the item"
7. Press "I'm done" button
8. Publish the page
If you have any problems, do not hesitate to contact us.
the Telerik team