Fasted way to opt customer in all at once.

Regarding getting my customers opted to the text registry. I have 1000 customers and I don't want to email or text each customer one at a time to get approval. How can send them all messages and upload the responses all at the same time. Also who and where do I upload the approvals. What does the accepted approval look like. Can it be email or a text thread asking the opt in quesiton then having the answer? How and where do we upload this opt in form to. Do we do it directly to the TCR or though ring central.?