There is a column on the overview named "tag". The tags your squad/wing/fleet commander sets will appear in this section. You need to open your overview settings, find the "columns" and select the tag column, then arrange it and other columns so that it is visible. (You only need enough space for one character width.)
Most help advice on overview settings often forgets or ignores the tag system as it is a tiny bit difficult to set a tag and anyone without a tag column on the overview (the default) will be unable to see it, but in my opinion the tag column would be great as the right-most column visible on your overview. Not only does it give the ability for you to see your FC's tags, but it also allows a small blank space where you can quickly see the EWar icons that the overview shows sometimes.
Edit: And Annie is correct about that tickbox. It is on the overview setting's "options" tab. Warning: you need to get used to a tagged ship suddenly appearing at the top of your overview because you may be used to sorting by name or distance and the slight difference might be distracting at first!
I would prefer FC’s just used the fleet option to broadcast a target, and then the fleet can just use the announcements in the fleet window to lock.