Here are the step-by-step instructions on how to use the topsoil calculator:

1. Enter Area Dimensions: Start by measuring the first area where you plan to spread the topsoil. Enter the length and width of the area in the provided fields. If your area has an irregular shape, approximate it to the nearest rectangle and measure the approximate length and width in feet.
2. Enter Topsoil Depth: Input the desired depth of the topsoil layer you want to spread in the "Topsoil Depth" field. This measurement should be in inches.
3. Add More Areas: If you have more than one area, click the "Add Area" button to create fields for the additional areas. Repeat steps 1 and 2 for each of these areas.
4. Select Topsoil Type: Choose the type of topsoil you're using from the "Topsoil Type" dropdown menu. The choices are "Clay", "Silt", "Sand", "Peat", "Chalk", and "Loam."
5. Calculate: Once you've input all the required measurements and made your selections, click on the 'Calculate' button. The calculator will compute the total cubic feet and cubic yards of topsoil required, the approximate weight of the topsoil, and the approximate number of pallets or truckloads needed.
6. Review Your Results: The results will be displayed below the 'Calculate' button in the "Results" box. It provides estimates for the total cubic feet and cubic yards of topsoil needed, as well as the weight and the number of pallets or truckloads.

Please note that these calculations provide an estimate. For more precise measurements or for irregularly shaped areas, you may need to calculate the area of each section separately and add them together.

Also, keep in mind that the depth of the topsoil layer can vary depending on your specific project and the type of plants you're working with. The topsoil calculator does not account for variations in depth across the area. It's always a good idea to check with a gardening expert or do some research on the specific needs of the plants you're planning to grow.