Looking at the Contacts app on two different phones running Android 12 and 7, there's an icon with a + in it floating in the lower right side. Tapping on it opens up the new entry window. Depending on the version of the Contact app your phone is running, it should be there.
Otherwise, if you use a web browser on a computer instead, go to
https://contacts.google.com
and there's a big + icon labeled 'Create contact' in the upper left panel. (Well this is assuming you're using Gmail, but the same principal applies if you're using MS Outlook, Yahoo Mail, AOL Mail, whatever. Just to the web mail page.) Personally I find it easier to create and/or manipulate my contact entries on a computer, but that's my personal quirk.