WordPress makes it easy to import from other sites, especially another WordPress site.
The first step is usually to visit your current site and use their Export feature. Then login to your new site and visit "Tools->Import" and find the appropriate importer and follow the instructions.
If you are importing an existing WordPress site, we have some tools to help that process. Make sure you read the full WordPress Import Instructions.
Note: if you will be using the same domain with your new BlogSites...
*Keep your domain pointing to your current site until you are sure ALL content has been transferred. If you try the import process, it might need to look at your current site. If you have transferred the domain and it is now pointing at our servers, your old site is not visible anymore.
**ONLY MAP YOUR DOMAIN TO US AFTER ALL YOUR CONTENT HAS BEEN IMPORTED.