Install XML-RPC for Textpattern 4.0.x

XML-RPC is an integral part of Textpattern, but initially disabled. To enable XML-RPC, log in to the admin side with publisher privileges and visit the “Advanced” page in the “Admin > Preferences” tab. Set “Enable XML-RPC server?” to “Yes” and hit “Save”.

Configure your client

XML-RPC endpoint http://mysite.com/rpc/
User Your Textpattern user login
Password Your Textpattern user password
API Blogger, MetaWeblog or MovableType (preferred).

Documentation