"Keywords" are the words most relevant for your page(s). It is not - as it once was (many years ago) a META-tag you add them to. There still exist a META-keywords standard but none of the major search engines support the tag anymore - they do not read or value the content in the META-keyword tag. So don't waste your time with that.
Instead, make sure the keyword(s) you want a page to rank for is actually used - in a natural way, on your page - in the TITLE, the main (top) headline, the body copy and URL. Do not overdo it. That does not help. Just use them in a natural way that read swell to users.
If you want to advance, then research how and why users search for that keyword and include answers to those requests.