Note: You can only message a creator you actively pledge to or have successfully pledged to in the past. If you are not a patron and wish to contact them for sales or press requests, you'll need to contact them offsite.
There are two ways you can message a creator you are supporting on Patreon:
From the "overview" section of a creator's page, click "more" on the left-hand side and then "message."
Navigate to the top-right of the navigation header while signed into Patreon.com and click the messages icon.
From there, you can click new message and enter the name of any creator you are a patron of into the text field to start writing to them:
Note: If you have been blocked by a creator you will not have any permission to message them.