Scopus is an abstract and citation indexing database. It tracks how different sources cite each other. Scopus does not search all possible scholarly sources. It chooses to index a select list of journals, conference proceedings, book series, etc.
You will need to create a personal account in Scopus to manage the alerts you will use to create your research diet. Scopus uses the same Elsevier account system as ScienceDirect and Mendeley, so you may have an account already if you use them.
To find a journal in Scopus, use the Sources option at the top. If you already know a title, use the default "Title" search. Otherwise, you can change the field to "Subject" to search or browse Scopus's list of subjects. In the result list, click a journal title to open its "Source details" page. You can also use the options on the left to limit results, such as to Open Access journals or highly cited journals. On the "Source details" page, click "Set document alert" to get emails when new articles are published. Click "Save to source list" to create a list of sources you use.
For a known author, use the Authors tab. You can search by name plus affiliation or by ORCID. You might find an author name by looking at articles you come across in your searches, are assigned to you, or who keep coming up in the reference lists for other articles you use.
If you are just looking for authors, try the Researcher Discovery search tab.
On an Author profile, you can set an alert to receive updates when they publish something new that Scopus indexes and if anyone cites them. These author profiles can be managed by the authors themselves and tied to things like an ORCID that validates the data. You can also save them to a list of authors.
You can get to a document page from a documents search, from Author profiles, and from Source details. Scopus uses a variety of metrics for analyzing how impactful a document is. Click "Set citation alert" to get notifications when a new document cites a particular document.
Searching the documents tab lets you look up new documents on a topic. You can control fields and add date ranges from the main page; on the results page there are a lot of ways to filter results in the left column. The results page also lets you choose to save a search for later and set a search alert that notifies you when new results that fit the search criteria are added to Scopus. From the results page, you can also get to document abstracts, Author profiles, and Source details pages to track any of those things.