This information is not relevant if you do assignments through a direct link.
Each course consists of number of modules. Once you selected the course you want to work on, you will see the module overview. For each module there is a card that contains some information about the module. Click on the module card to see the assignments in it.
Modules can have a start and end date and time. You can only work on the modules between these dates and times. Modules for which the deadline has passed can still be inspected. Modules that are not yet available cannot be inspected. In the screen you are warned about upcoming deadlines for modules. There are filters to hide the past modules, the modules that are not yet available, and the modules you completed.
To make assignments in a module, click on the module card. You are now shown the list of assignments in the module. When you have done all mandatory assignments in a module, the module becomes completed, which is clearly indicated. You can still make optional assignments in completed modules or inspect your answers.