Assist pls-how to merge 2 images

[Low_tech_gimper]

Thank you. It worked! The images are configured as I want them, but there's some artifact around the person's hair (some brightness in her hair & a bit of the checkboard) that needs to be corrected. What tool & steps would you suggest to correct? Finally, could you please tell me how to save this & what format (png?)? I ultimately want to send this image to Costco for a New Year's card.  Thank you again for your patience & assistance.