To share a layer, select it in My Layers and click Share. The following window will appear:
To share/unshare a layer with a specific user, click Individual user and enter the e-mail address under which the user is registered in GAP. Then click (Un)share.
To share/unshare a layer with a certain community/group, click Community and select the community from the drop-down list. Then click (Un)share.
To share a layer with all GAP users, select Public and click Share. If the layer is already shared, you can unshare it by pressing (Un)share button.