Open SolidWorks 2020, and select a new part. Don't forget to save your file frequently as you go.
Step 1: In the bottom-right corner of your Solidworks window, change the units to MMGS (millimeter, gram, second).
Step 2: Select the Front Plane in the design tree (the left column on your screen) to begin your sketch. Click on the Sketch tab above and click Sketch.
Step 3: Make a vertical line starting from the origin. Then use the smart dimension tool to make it 3mm tall. Follow the same process to draw 2 more lines stacked on top of one another, and make them the lengths shown in the screenshot below. Make the inner line a construction line by clicking on it (after exiting the Smart Dimension tool) and hovering over the icons until you find the "Construction Geometry" icon. After clicking it, the line will become dashed.
Step 4: Make a horizontal line starting from the origin. Then use the smart dimension tool to make it 6mm long. Draw another horizontal line next to it with the length shown in the screenshot below. Make the second line a construction line by clicking on it (after exiting the Smart Dimension tool) and hovering over the icons until you find the "Construction Geometry" icon. After clicking it, the line will become dashed.
Step 5: From the right end point of the horizontal construction line, draw a vertical construction line with the length shown in the screenshot below.
Step 6: At the top of your sketch, draw a 1mm horizontal line at the location shown in the screenshot below.
Step 7: At this point, you should have a total of 4 solid lines and 4 construction lines that look like the screenshot below.
Step 8: Use the spline feature to connect 3 points on your sketch and create a side profile of your egg. Order does matter, so click sequentially from top to bottom or bottom to top on each of the 3 points. Press Esc to finish the spline. You'll notice that it doesn't really look like the side profile of an egg yet, but we'll fix that shortly.
Step 9: Now, you are encouraged to use your creativity to tweak the side profile of the egg to your own taste. I'll give a couple suggestions for how to tweak the spline for best results, but you are welcome to change the lengths of any of the construction lines to get different results. When you have the spline selected, you will see "adjustment arrows with diamonds" that are tangent to the spline. They can be manipulated to change the shape of the curve. You always can press ctrl-Z to undo a change and revert back to the spline's previous shape.
If you zoom into the top of the egg, you'll notice that the spline connects to the 1mm horizontal line at an angle (see the first screenshot). We would like the spline to be approximately horizontal at the point of connection with the 1mm line. This will give the appearance of a nice continuous curve, but it doesn't need to be exact. To do that, pull the Smart Dimension of the 3mm line over to the right side to give yourself a reference. Then move the adjustment arrow thing from the spine parallel with the Smart Dimension reference line (see the second screenshot).
Step 9: Zoom into the bottom of the egg and perform the same operation on the intersection between the spline and the 6mm line. Again, the goal is to make the spline approximately horizontal where it connects with the 6mm line to maintain the continuity of the curve.
Smart Dimension the line to 45 degrees from the vertical construction line.