Watermark upload not possible; vanity URL approved

We have created the necessary vanity-URL last week and it is approved but we don't see the field for uploading a watermark image like described in this article: 
https://support.zoom.us/hc/en-us/articles/360000921326-Hinzuf%C3%BCgen-eines-Livestreaming-Wasserzeichens

My user account has admin permissions. 

Any ideas?