As we explained in our introductory articles to StumbleUpon, the website is meant to be a way to discover new content on the Internet, not to search for something specific. However, StumbleUpon does have a few limited search functions. You can explore popular pages within a certain interest, or you can search for a certain interest, user, or list.
How to search within a certain interest
Go to www.stumbleupon.com in your web browser and log in.
Click on your profile picture in the top-right corner, and then click on Settings, Add Interests, My Friends, My Lists, or My Likes.
From any of these pages, click Home.
Now, click in the box with the magnifying glass inside it (it will say "Explore an Interest") and type in something you're interested in. Then select an option from the suggestions that appear by clicking on it. (If you press the "Enter" key on your keyboard to try to search for exactly what you typed in, StumbleUpon will just pick an interest that most closely matches what you typed in.) From there, you can click on a piece of content that you're interested in.
How to search for an interest, user, or list
Follow steps 1 and 2 in the "How to Search within a Certain Interest" section above.
Now, instead of clicking Home, click Follow instead. From there, you can click Interests, Stumblers (i.e. other StumbleUpon users), or Lists to select what you want to look for, and then click in the box that says "Search" and type in what you're hoping to find. Then press the "Enter" key to see what results StumbleUpon gives you.
NOTE: You can also click the Channels option to see official StumbleUpon lists of web pages that revolve around a certain brand or celebrity. However, they cannot be searched, though you can sort them by brands, people, or those that StumbleUpon recommends to you (based on your activity on StumbleUpon).
From there, you can click on an interest, user, or list to see content within, or click Follow to see more from that interest, user, or list.
That's a quick primer on how to search for things on StumbleUpon!