Evernote Cloud API (legacy EDAM)
Go to Developer Token, click Create a developer token, and copy the value starting with S=. Evernote says developer tokens are currently unavailable except for proven necessity and recommends OAuth for most integrations. If you lose the token, return to the same page, revoke it, and generate a new one. See Developer Tokens.
Use the Evernote developer portal at Legacy API to get an API key (oauth_consumer_key) for your application, then implement Evernote's OAuth 1.0a flow from OAuth: request a temporary token from https://www.evernote.com/oauth, send the user to https://www.evernote.com/OAuth.action, and exchange the authorized request token for an access token. The docs explicitly say “If you don't have an API key (oauth_consumer_key) you can get one here: Get an API Key`.”