Not all API's use OAuth. Less than half of the currently integrated apps do. Mostly the major apps use it, e.g. Google, Twitter, etc.
Here is an empty key file: empty.keys
This file is where you find info to obtain the keys and where you enter the keys and account information you used to obtain the keys. You can then import your keyfile into the system.
To know which apps need oauth keys, look inside the keyfile.
Here is a sample entry for the 500px app:
<key>500px OAuth Consumer Key
<desc>The OAuth consumer key provided to you at http://500px.com/settings/applications when you sign up for a developer account.
<key>500px OAuth Consumer Secret
<desc>The OAuth consumer secret provided to you at http://500px.com/settings/applications when you sign up for a developer account.
The way to go about it is to look in the description to know where to sign up for the app. You need to create an account to register the app, so you can place the username/password for the account in the comment blocks: <!--account>username/password<account-->
Then you have to fill out an application form to obtain access to their API and agree to their terms of service.
When an application form asks for the "oauth redirect uri", you must use this value: https://yourdomain.com/oauth
For example, for the dev.apiant.com system the oauth redirect URL is https://dev.apiant.com/oauth
The app will provide two oauth keys. Put them into the <val> nodes like is shown with XXXXX and YYYYY above.
Then to load the keys into your system, sign in to https://yourdomain.com/admin-console and go to the System Keyvault page. From there, open the keyvault and use the Import button to upload your keyfile.
Your keyfile is very important. You will want to keep it handy and safe.