In order to upload a list of phone numbers and directly send them an SMS campaign, you must go to Data Sources > Add Data Source and choose the CSV or Copy and Paste option.

It's important to select the country to which the numbers belong to correctly format the phone numbers. Click 'Continue' in all the following steps.

You will have the numbers available and the option to send a campaign.

For sending the next campaign, it's important to note that deleting this data source and uploading new numbers will be slow. Therefore, we recommend uploading a new version, which means updating this data source. Don't worry if all your new numbers are different; updating the existing data source is the best solution.

Refer to this article for how to send subsequent campaigns