Once trademark or service mark status is granted by the USPTO, the mark is considered “registered”. At that time, you may then begin using the ® (R in a circle) designation with the mark.
Until then, it is illegal to use the ® indicator, and instead you may use the ™ indicator when the mark is used with goods and the ℠ indicator when used with services. Although not required, your specimens of use should show proper use of the indicator.