On the page Events, subtab Events, choose an event, in the row, far right side, select the button Select.
If not registered as a venue (e.g.: planner, caterer, host), add a venue.
On the tab Details and subtab Vendors, select the option +Add Venue.
In the pop-up window, in the search field, type at least the first three letters of the venue name.
Select the icon Search.
In the pop-up window Add the Venue, next to the venue, select the button Select. (If the venue isn't listed, at the bottom of the pop-up window, invite the venue to share the event. Select the button INVITE.)
In the next pop-up window, select the radio button Ok, and send a notification Email to the venue or select the radio button Not now, maybe later.