You select one of your projects through clicking on those 3 dots or on the field on the top right of the project. After you selected it, you click on the trash bin on the lower right corner.
Deleted projects remain available for some time, so they can be recovered. After a certain time, which can be set up in the settings, they are deleted permanently. You can also permanently delete them yourself. For that you have to go under “Deleted” as filter option and choose the first trash bin icon on the right. The icon below it allows you to recover the deleted projects.