If you're wanting to research adulthood, SocIndex is a great resource to use (linked to the right).
When developing your search strategy, it is helpful to brainstorm variations or synonyms of the key concepts you're researching. For example, based on the suggestions from your syllabus, if you are researching sexuality, you might try different combinations of the following search terms:
sexuality OR sexual orientation OR gender identity
You might choose more specific topics, such as: bisexuality, open marriages, gay couples, etc.
Remember, research is a process! If you need any help, feel free to email me at firstname.lastname@example.org!