These are a few step-by-step lessons, to get you started. SolidWorks is a very powerful and professional-grade complex program, and you can discover many more features, from its own manual pages, or from online discussions among designers and engineers.
You can for instance define a pattern to be repeated along a line, which then can replicate some feature. Let’s say we want to add interior ribs:

We can do this by first sketching a small circle in the cylinder top face, centered somewhere on the interior edge. Then we extrude it, and then we replicate it all around the cylinder. How do we do that ? We first select the extrusion (from the left list, for instance), then we go to the ‘Linear Pattern’ drop-down button-menu and select circular pattern

and then we select the inner edge as direction, how many instances (it starts with 2, and the yellow preview shows an increasing number as we go to 3,4,etc, we can also specify the angle between two instances, etc), and then we validate.
There are ways to 3d build from a sketch to another, even if they are not the same — this is called a ‘loft’.

This simple example from here was made by
- Inserting another plane:
- In the ‘Insert’ top menu, in the dropdown, select ‘Reference Geometry’ and ‘Plane’
- Clicking on the ‘Front Plane’, and letting SolidWorks guess that we want the new plane parallel to it
- Specifying for instance 2mm for the ‘offset’, and toggling ‘Flip offset’, to have it “outside”
- Then sketching circles in each of these planes
- Finally, requesting the ‘Loft’ and clicking on each of these two circles


In order to do a good job, many times we want to align holes, or elements sticking out, so that can be done with measures on what we are building, or by using construction lines of precise lengths (which we enter in the side dialog). There are many geometrical features, which can be used to help anchor the elements.
There are several types of holes, and there are ways to extrude along closed or open lines (revolved boss/base, etc).
Finally, there is the ‘assembly’ mode, where several parts can be imported to be put together, and can be mated (by aligning holes, by offsetting faces or making them coincide, etc). As mating elements are added, SolidWorks allows you to move the parts with the mouse pointer, subject to these constraints, and of course checks if something becomes incompatible. If dimensions are cleanly and correctly set up, then such alignments will work and you should be able to rotate parts.
There is also a very large library of predesigned mechanical parts, such as screws, nuts, and even gears, which have specific parameters. They can thus be imported, configured, and, when 3D-printing them, if a good resolution is used, the mechanism will be fully functional.