Frame or not?
Works on canvas generally doesn't need a frame. Keep that in mind when purchasing a hung canvas. I suggest you first hang it on your wall and see if you like it without a frame. If the size is appropriate you can also place it on a shelf leaning against the wall.
If a frame is the look you are going for, I recommend searching out local framing stores in your area. If you have purchased an original painting you might prefer to find a perfect frame that fits the style of the painting. If so, your local framer will have a ton of options, plus will help guide you in the process.
There are other options for your hung canvas, including the ones listed below for paper prints. If you are purchasing a print on paper, there are simple solutions ranging in price. Paper prints can be easily put into a store bought frame or taken to a framer. I again encourage you to seek out a local framer in your area if that is within your budget.
There are a variety of frame styles, and mats, out there and it can be fun for you to find one yourself that exactly fits your design style. You can always search stores in your local area and online for frames... including your favorite stores. IKEA is a good option for small inexpensive frames. Hobby stores, such as Michaels or Hobby Lobby, are good places to check out. Stores like Ross, Marshalls, TJ Maxx or HomeGoods often have frames available. And of course Amazon has many types of frames including magnetic poster hanger frames, which can be an easy and inexpensive way to hang your paper prints.
Plus, check out Framebridge - unique source that my artist friends have recommended (https:/www.framebridge.com).
If you would like to keep things simple a basic white, black or natural wood gallery frames always look great with every décor style. These can be found easily online or at a local store.
There are a ton of colors available at your local framer if you are looking for a show stopper piece. I recommend searching out a local shop or asking for recommendations from a local friend on who to use. Framing shops are experienced in helping find the perfect frame to go with your art.
And again keep in mind that canvas paintings stretched on wood bars do not need to be framed unless you desire.
Overall have fun with finding a frame you love while keeping in mind that a frame can be changed out to fit your decor at a later time.
Hope this was helpful.