You learn by doing, and Undergraduate Research Opportunities are how you do research at CMS/W as an undergrad.
MIT’s Undergraduate Research Opportunities (UROPs) are meant to connect students with faculty research. Arranging one for yourself with CMS/W can take a couple different paths. The most common is to have a great idea, related to CMS/W research or faculty interests, and approach a faculty member directly about his or her becoming your UROP sponsor. The other is to check out the list of available UROPs proposed by faculty—think of them as job openings—and apply.
A UROP can be for pay, for credit, or as a volunteer. Whichever it is, your work and CMS/W’s obligations to you use the same standard: the research done “must be worthy of academic credit”.
UROP proposals are welcome all year long, though there are deadlines.