How to transfer posts to new user account

I added a new user(admin) to each of my wp blogs. I don’t know how to do the next step, “transfer all the posts to that account” I will wait to delete the old user account until I get some help. Thank you!

Here are the directions from the Codex:
Don’t use the ‘admin’ username
The majority of attacks assume people are using the username ‘admin’ due to the fact that early versions of WordPress defaulted to this. If you are still using this username, make a new account, transfer all the posts to that account, and change ‘admin’ to a subscriber (or delete it entirely).