Can I use videos in youtube ?

can i use videos for my youtube channels, If yes what information we have to give in video discreption?

In general yes. The purpose of creating a channel in YT is to upload videos and you have to provide related description for the video. If the video is about advertising, sports, gaming etc. you got to write some good sentences and maybe put a link or two in the description. and If no, just a general information about the video.
What I’d like to do is creating a thumbnail for my videos. So, when people see your video and before clicking and opening it, they see a nice and attractive thumbnail and maybe you can gain more viewers this way.

You can buy a license and use the video on youtube channel. Single license - for one video, multiuse license - for infinite number of your videos. It’s not mandatory to give the author credit.