The number of CAD softwares on the market has increased dramatically in the past few years, but Solidworks and Onshape are still the best known.
One useful analogy is to compare Onshape and Solidworks to Google G Suite and Microsoft Office. Brett Goldfarb with Boulder Engineering Studio explains "Solidworks, like Office, is primarily a dedicated application that is installed onto your PC and is often considered a more powerful tool when compared to cloud based alternatives (like G Suite). Onshape, like G Suite, is a cloud based application which requires an internet connection to be run through a browser but has the inherent benefits of existing on a shared access platform." His full article dives into specific differences and implications when sketching.
Essentially, Onshape is slightly simpler and superior when collaboration and ease of access is a priority.
Follow this link to their website: https://www.onshape.com/en/
From there, you can create an account and get started!
Onshape's Learning Center provides a variety of courses that delve into various aspects of the software. Their self-paced courses are great for one who thrives on figuring things out with minimal guidance. Find it in the top right corner of your home interface.
CADSessions is another great resource. On their Youtube channel, you will find both tutorials as well as videos that delve into specific topics. Their "Onshape Beginner Tutorials" playlist guides you through the creation of a part using multiple tools within the program.
Once you have a basic idea of what you're doing, reach out to your classmates with specific questions! They would be happy to help .
When starting in Onshape , you begin with a flat sketch of your piece that you can then extrude. You can overlay different parts and sketches in a 3D simulation of how your parts would fit together. You can also create assemblies. Assemblies are a place to join different pieces to see how they interact and fit together, its especially useful for scaling.