How to use csharp corner properly?

As Sam sad, there is a Code tag/option in the editor. Click that and paste code there.

in your myaccount section, you will find the template and guidelines kindly download and go through that.

Can you explain what you mean by code section? Are you asking how to upload source code or do you mean you want to post code in the article? To post code in the article click the code snippet

icon then a box will be shown for you to enter code. There might be a different way to do it but try that way.