There are a number of no-cost products available for file validation and hashing that have point and click interfaces. Here are links to a few of them:

Follow the instructions provided to install the program. When you run the program, use the file selection tools provided to select your downloaded ISO image files. Then select the SHA256 algorithm for calculation, and run the tool. The program takes some time to complete, since it must read the entire ISO file.

If you are using HashTab, you will need to enable the SHA256 checksum option. In order to do this you will to open the File Properties window (right click --> File Hashes tab --> Settings), then select the SHA256 option. It is advisable to uncheck any preselected hash options as they will only slow down the hash calculations.

Open the file CHECKSUM with a text editor, such as Notepad, to display its contents. Make sure the hash displayed by the hash tool for each of the downloaded ISO files exactly matches the corresponding hash in the CHECKSUM file.

If all of the hashes match, you can burn the ISO file to disc. If a file does not match, download it again.