1)

Add proper URL rules and select "Validation & Tooltip" from the options

2)

Capture an element, add a guidance message and customize the icon if you like

Capture an element, add a guidance message and customize the icon if you like

3)

Select tooltip icon position from here

Select a validation type for the captured element

4)

We will select "Mandatory field" as the option

5)

Enter a validation message

Customize the position and action of tooltip

6)

Click "Save"

7)

Publish this tooltip and it's respective parent folders

8)

Hover over the tooltip 

9)

Here is the tooltip in action