You are attempting to import a program into your instance but you get the message "The tokens (lead.example) are not available in the destination subscription. They are either custom fields that you have to create or need to be synced from your CRM system, if you use one."
Tokens referencing fields that do not exist in the destination instance cannot be imported. You will need to remove all references to those tokens from the program, as well as from all the assets that are contained within it.
Tokens can also exist in the text versions of emails, or within the templates that emails are based on, and not appear within the HTML version of that email. These tokens will also prevent program imports and must be removed.