Depending on how you will be integrating with the API you likely will not be using all of the available features. This makes it important to know how you will be using the API. For example, in many cases you won't need to worry about OAuth and access tokens.

Setting up a designed videosite with my own branding, my own content, on my own domain:
This is the core promise of TwentyThree, so you won't even need to use the API to achieve this goal. Consult our Help Center for information on how to get started.

Re-using data from a public site to display thumbnails or embed videos:
In this case, you can skip OAuth entirely, an simply retrieve lists of content. Be sure to to understand response formats, pagination and the limitation of anonymous acess – and then simply refer to the method documentation.

Using the TwentyThree site as a private archive for video:
Here, you will need OAuth signatures in order to sign requests to the API. You need to be confortable with the flow of OAuth, find a good OAuth library in your language of choice, and know the the API methods. You should create a set of privileged credentials from the backend of your site under Settings → API & Application to access the API.

Allowing user uploads to the TwentyThree site:
Again, you will need OAuth signatures, but you can use privileged credentials from Settings → API & Application in the site's backend. You have a choice between server-based or browser-based uploads, and you should understand the concept of webhooks.

Having the user log in to their TwentyThree site site to grant you access:
This is the only case where you will need to worry about the OAuth authentication flow (since you can use privileged credentials otherwise). Along with everything else, you need to decide on a permission level to authenticate users at.

Giving visitors access to content through SSO or a paywall:
Users can be granted access through single sign-on which will grant them access to the content on an entire site. This aproach is designed to grant users full access to a site, it's content and the features afforded by the TwentyThree templating engine. Be sure to read the article on Single Sign-on Integration if you wish to know more.

As is clear from this list, the TwentyThree API can be used to achieve vastly different goals in different contexts. If you unsure on how to approach an integration, just ask us.