Good cel of Megs. How much did it put you back?
About your question how to store, temporarily remove it from the existing cel back and/or matting if it included one. Replace them and put the cel into a archival quality cel bag. Think larger comic or magazine bags if you need a visual reference. You will need to cut some of the corners to allow the fumes to be released and to allow the cel bag to release the excess air. Also since you are in the limbo process of framing your cel, you will need to know some facts about production cels:
1) Keep your cel AWAY from any sunlight and/or artificial light. Yes that means no overhead lighting as well. Why? B/c the light will cause the tracelines to fade. What are tracelines? Those are the blacklines around the paint which were historically made by inserting the acetate into a xerox type of machine. On one side you had the black tracelines and the other the paint is applied manually.
2) Keep your cel isolated from other items. Specifically do not allow anything to rest on top of it or next to it. NO PRESSURE must be placed on top of it. You can slide it into a large ITOYA brand folder if you like (many cel collectors use these for storage and they come in varying sizes) and keep it either upright like a book or with the spine pointing up. Why? To release pressure and so it enables you to hang the entire folder on a sturdy wooden or steel hanger.
3) Isolate it away from moisture, smoke, cold and heat. The best place typically is in a closet in the furthest corner away from sunlight and/or heat/moisture from the outside or the bathroom. Another way to reduce the moisture is to use the small packages commonly found with computer parts, shoes, and even in food, Sylica something. These reduce moisture build up and if you really don't have any get some kitty litter put in into baggies and use those instead, it works.
4) Insure the cel ASAP! If you paid anything close to 1k you need to insure that cel.
5) Do a lot more research on the TF cel market b/c it is not for the faint of heart, poor credit or low of funds. Know and understand that most high end cels RARELY IF EVER leave collections. Having said that do not be surprised not to find anything for choice popular characters and if they do appear expect to spend upwards of 7k easily.
6) Eventually even when you do get your cel professionally framed with archival acidfree matting AND UV resistent glass STILL DO NOT allow direct sunlight or lighting be exposed to your cel.
Anyways if you need more information PM and yes I do collect traditional animation production cels as well. Welcome to quite possibly one of most expensive addictions since crack.