You can Tag an organization by going to Investors > All Investors, My Shareholders or Peer Comparison, clicking on the Name of the Investor in the first column, can be a fund or an institution, then once entering the profile, see your Tags displaying in the first part of the profile. You can add one or several Tags by clicking on Add Tag. You need to type your Tag in Type to Search and then create it. All your Tags will be reflecting in the part Tags. See below:
To remove your Tag, just click on Remove, the small cross next to the Tag