You can add a tool tip or instruction to a field on your Marketo form so that users have more information about what you are asking them to input.
1. Select a form and click on Edit Form.
2. Select the field you want to add an instruction to.
3. Under Form Properties, Field Specific, enter the Instructions.
Awesome work! Now when a lead hovers the cursor over the form field, the tool tip or instructions will be displayed.