Protecting Your Art
Prints are delicate and should be handled with care, this means avoiding touching the surface of the print as much as possible, do not store or display your print in humid locations or direct sunlight. 

Having your artwork professionally framed is the best way to make sure it is protected for the long run, it's also best for larger sized prints which can be trickier to frame at home.

Framing Materials
Acid free framing materials, such as an acid free mat and backing will help preserve the print, UV coated Acrylic or glass is recommended if the art will be placed in a sunny location. 

Certificate Of Authenticity
These generally come in a plastic sleeve, like art prints they should also be stored away from humidity and sunlight.

Custom framing is generally the best way to go to create the perfect, final piece. If there are local frame shops in your area, it's worth contacting them to get a few quotes especially for larger size prints which can be trickier to frame at home.
Refer below for online framing options. 

A frame shop can cut a custom mat to fit any print size and frame. If you already have a frame that is larger than your print but only need a mat, it's best to bring your frame and the art print to a framer and they can cut the correct size mat for you.

USA Online Framing
American Frame - Frames can be configured to your exact specifications and purchased as a kit to assemble at home, simply enter your print size, no need to worry about which size mat or frame to buy.
Simply Framed - Mail in your art for custom framing or purchase their DIY frame kit to assemble at home.
Frame It Easy - Affordable frames that can also be configured by entering your print size.

Please note, I am not affiliated with the above companies and cannot guarantee their framing services.