How to add text about discount codes?

Shopify Partner
14 0 2

My client has a brick and mortar store in addition to selling online. She would like to add a message to her checkout page in regards to discount codes: Coupons or Discounts can only be accepted with In-Store purchases, not on-line. Please call XXX-XXX-XXXX with questions.


Is that possible? If so where would I enter that text? Would it be under edit languages or in the edit code?