The best way to introduce your customers to the new Loyalty Program you have just established is through SMS and Email Campaigns.
All you need to do is go to your Regular Campaigns and create a New Campaign, like it shows below.
The Email Campaign can be more detailed with all of the Loyalty Rewards listed along with the different ways of earning more loyalty points.
The text campaign on the other hand should be short and straight to the point with the [share_page] variable added, so your customers can enter the Loyalty Program with their phones.