Unable add tooltips beside the project field in expense report page

Summary:

Hi,

I am trying to set tooltips beside the field like the example screen below to put some customized notes besides the “Project no.” in the expense page. I try to enter to the sandbox and wanted to add the text beside the project number. But it is not editable. Is the project no. field able to add the hover over text description? Besides, how can i add a question mark icon beside the field with the hover text? So that people are aware there is a text there? Example as below:

Content (please ensure you mask any confidential information):