Scopus is indexing selected journals automatically, and there is no way to add papers manually. The Scopus database of papers is rather incomplete, and my impression is that they neglect many journals that are not published by Elsevier - perhaps to urge authors to publish in Elsevier journals. See also https://www.researchgate.net/post/Does_anybody_know_how_we_can_add_the_missing_citations_to_our_profile_in_Scopus
You cannot simply put your articles in Scopus unless the journal in question has been selected by Scopus for indexing. Scopus database is owned by Elsevier, an international publication group, and they have specific content policy and selection criteria for the journals to be included in Scopus. For more information on journal selection criteria please visit: