If you're a Microsoft employee, please leave a comment, and we'll add some instructions for you (we'll figure out what instructions are best for you, since there are existing instructions already).
But this topic is more for the community (people who are not Microsoft employees). 
You must be a Microsoft employee to create a blog.
But non-Microsoft employees, Contractors, and others can join a team blog that's being run by Microsoft employees. Because most team blogs represent products, those blogs are typically only run by Microsoft employees (occasionally with Contractors added as authors). But other blogs exist to represent the community, such as the TechNet Wiki blog or MVP blogs about a specific technology or language/area.