I am guessing that you are on the Event Details layout, you've selected the Guests tab and you want to add a guest for this event?
If so, when you click the + button or just click the guest field (all this + button does is put the cursor in this field) , you should see a drop down list of existing contacts appear and you can select a contact from this list. This does not create a new contact record, it creates a new link to that existing contact record in the Guests table--a join table that links the current event record--to the selected contact record.
Thanks for your reply. I am on the Event Details Layout but I have deleted tabs I do not need such as Guests and Tasks. The only tabs I have left are the Event Details Tab and the Contacts Tab.
From the Event Details tab, I click the + at the bottom to add a new contact and it changes to the 'Contacts' layout tab. From here, I either enter a new contact associated with an event or I want to select an pre-existing contact who I have entered previously for another event buit it's this I'm having problems with.
Once I click on the + symbol and it takes me to the Contacts tab, it puts the cursor in the first name field but there are no drop downs that appear that would allow me to select a pre-existing contact.
There shouldn't be any such drop downs as you are creating a brand new contact record.
To add an existing contact to the list, do not click the + button. Click on the Name field. Hidden behind the name field (which is set to not allow access when in browse mode) is a drop down list which deploys when you click on the name field--where you select an existing contact and the drop down then enters the contact's ID number to establish a link between that contact and your current event record.
Thank you very much again for all your help Phil. What a simple solution - I can't believe I didn't think about trying that before (I feel slightly silly now)...Oh well, I'm just so pleased I now have an answer for something that has been frustrating me for a little while now!
This is the solution from which I learned the trick of hiding an ID number based drop down field behind the name field from a related table...