Generate and download a part you need for your project. You can afterwards 3d print the part for your diy project or use it as a placeholder part in an assembly in digital form.
Make sure that the part meets the requirements of your project before use, especially if it is going to be 3d printed. You should take into consideration, that 3d printed parts are going to be far weaker and less precise than traditionally manufactured ones. You are only allowed to use parts generated with this generator, if a failing part is not going to lead to a safety hazard or break other parts.