Contact your local Post Office (if you sent via USPS), or whichever carrier you sent it through, for an answer to your question;  but I don't believe you can add tracking/D.C. to a pkg AFTER it's been shipped.  It might be possible if you were able to get back to the P.O. before the pkg. was processed and left the facility...if it were still sitting in the back room waiting to be processed they might be able to retrieve it and let you add the Del. Confirmation service, etc. -- but if it's been a day since you shipped it, then it is already on it's way and I think the short answer to your question is: NO

I reserve the right to be wrong.