1. Open Watermark and click Create Watermark.
2. Choose where it applies: All Accounts, or one connected channel.
3. Choose the Watermark type:
4. Text: for example @yourbrand, with style, color and weight;
5. Image: your logo, chosen from your Files.
6. Set Position, Size and Opacity and check the Live preview.
7. Click Save Changes.

From then on, pictures published to those accounts carry the watermark. A watermark set for one channel takes the place of the one for all accounts.