That is a great question, and the answer is actually quite simple. To mail Christmas cards, you will need to purchase some holiday-themed stationery, such as envelopes, cards, and stamps. First, you will need to address each envelope with the recipient's name and mailing address. Then, you will need to place the card inside the envelope and seal it. Lastly, affix the stamp to the upper-right corner of the envelope and drop it into a mail collection box or take it to the post office.