For youtubers, how can the youtubers design intros and outros(the beginning and end) for their videos like what most youtubers do?

May I ask what you will use to create the video? You posted your question in the Adobe Captivate forum, and I don't think you'll be using that rather complicated app for your video.

There are lots of different kinds of software and variations that will allow for that.

Were I to do it, I'd use Camtasia:

http://www.techsmith.com/camtasia

It not too expensive, not too terribly difficult to learn, and pretty good with those kind of features.

Adobe Spark seems like it can do it too, but I've never tried it:

Free Custom YouTube Intro Maker | Adobe Spark

If you want something cheap and easy, you can select and do basic customizations from sites like listed here:

10 Ways to Create YouTube Video Intros & Outros • Kevin Muldoon

That may be a good way to start but always good to create your own from scratch and gain the skills