In step 3 of the assessment settings, you will need to edit the visibility. Here are the steps:
Same configuration - Where the settings you previously set will remain the same
All Sections:
Publish on click - Publish and unpublish the assessment whenever you want. You can make the assessment visible to all your learners. Finally, you need to set the assessment's time limit (meaning when learners launch it, the time you set is the time the assessment will take to stop allowing answers - the end of the assessment)
Scheduled publish - Set a date and time limit for the assessment
Scheduled publish with duration - Set a date and time limit for the assessment, with a time limit in which the assessment ends after the learners launch it
Click on Next
Next Step: