Locate the activity, resource, or section/topic in your course that you want to ONLY be available after a student has completed a select activity.
If Edit mode is on, click the Edit menu, then select the Edit Settings or Edit Section option.
Click into the activity or resource and then click Settings from the Secondary Navigation.
Scroll down to and expand the Restrict Access section.
Click the Add restriction button.
From the popup list, select the Activity completion option; it should be located at the top of the list.
Ensure that Access restrictions are set to:
Scroll to the bottom of the page.
Click the Save and return to course button.
When restrict access is applied, you should see the activity greyed out with a note to students as to what needs to be done first.