In-text citation format
APA uses author–date parenthetical citations. The author is whatever appears in the author position of the reference list entry - usually the uploader, sometimes a channel name, occasionally a username.
Paraphrase
Behavioral nudges can quietly shift weekly routines (Okonkwo, 2023).
Direct quote with timestamp
Okonkwo (2023) describes the pattern as "a thousand small permissions we never remember granting" (2:15). Timestamps replace page numbers for any audiovisual source.
Username as author
(Veritasium, 2020) - usernames in the reference list become the author name in-text, with no quotation marks and no italics.
Organization channel
(TED-Ed, 2021) - when the channel is the uploader, the channel name is the author for in-text purposes.
No date
(HistoricalArchives, n.d.) - the abbreviation occupies the date slot.