With editing turned on, in the topic to which you want to add your new assignment, click on Add an activity and choose Advanced uploading of files. Now, you are at the Editing assignment page. There are many more configuration options for this activity compared to an Offline assignment, but for now I'm just going to worry about the important ones. Remember, for more information on specific settings check out the Moodle docs for this page link at the bottom of the page—and you can always come back and change settings later on if you need to.

Give your assignment a name and fill out the description.

Use the Grade setting to specify the maximum grade you are going to give for this assignment. I'm going to leave the Grade setting at 100 (meaning I can grade this assignment out of 100). Maybe your assignment forms part of an overall mark and you need to mark it out of less. You can even choose to create your own custom grades (e.g...