Connect any Twitter accounts that you would like to use with Tweetbot.
Once you're done, copy the Integration URL from the Dashboard into Tweetbot for Mac or iOS.
On the Mac, navigate to the Tweetbot Preferences, select the Account tab and choose Custom for Image Upload. Copy the Integration URL into the API Endpoint field, and you're done.
On iOS, navigate to the Tweetbot Preferences by tapping on your Profile Picture in the top left when on the Timeline tab, then tap the Preferences button in the bottom left of the account overview. Navigate to Account Preferences and select your desired account. Tap on Image Upload and select Custom. Copy the Integration URL into the API Endpoint field, and you're done.