What is the easiest way to design from an image in solidworks?

When designing from an image reference, it is important to have a picture of the Elevation, Plan & End View (XYZ).

When starting to design, it is best to first set up construction lines/boxes with the dimensions that you wish for the end product to be. Then when in sketch, you can import a picture (type "sketch picture" in the search box top right if you can't find it).

When the image is imported, I recommend first downscaling/upscaling the image itself to fit within the construction lines, and then if you want you can adjust the blue length line to the image (put one point at each end of the product you are tracing and then input the dimensions).

Repeat the last step for all 3 orientations (Elevation, Plan, End View / XYZ) and then you will have your reference set up.

In terms of actually tracing the part and getting a solid body, if the object has simple geometry you shouldn't struggle too much, however if there is a lot of curvature that moves through different elevations, its best to use the surfaces features.

If you end up using surfaces, its best to make a couple of different planes so that you can adjust the body of the part at different sections, and then at the end when you're happy with your design, you can convert surfaces to a solid body (if needed).