If your campaign has a form, it should have an email field by default. If not, you can add an email field by clicking Add Form Field, then selecting Email.
The field will be added to your form and a slider menu will open on the left where you can edit the label and placeholder text, and make the field required.
In the left sidebar menu, you can click the six dots to the left of the field and drag up or down to reposition the field on the form, or use the “trash can” icon to delete the field.