This is very simple to do. You may need to add a new administrator user if you’re not the only person writing for or managing your wordpress.com blog. Or if you have arranged for someone to move your wordpress.com to self-hosted wordpress then they will need administrator access to export your content and make any configuration changes required.
Step 1. Log in
You need to be logged in to your wordpress.com account if you aren’t already.
Step 2. Go to the WP Admin Dashboard
Open up your blog in a browser, and use the My Sites header at the top left to go to the WP Admin dashboard.
Step 3. Invite the new user
From the dashboard, go to Users -> Invite New
Step 4. Fill in the new user details
You need an email address for the person you are adding as an administrator for the blog, then select the Administrator dropdown option. Finally, hit the ‘Send Invitation’ button.
Step 5. That’s it!
An email will be sent to the person you have invited, and they will be able to add administrator access for your blog to their own wordpress.com account.