To make sponsors visible in the mobile app and the sponsor widget on your website, assign them a label that has the following checkbox enabled:
✔ "Sponsors with this label will be displayed on the web page and in the mobile app."
If sponsors have a dedicated subpage on your website, also enable:
✔ "Sponsors with this label will have their own subpage on the web and in the mobile app."
✔ On the sponsorship tab, "Sponsor has an own sponsor page (if sponsorship level enables it)" has to be checked as well.