Not sure if I understand correctly - You need to use the keywords within the website content. I recommend a site like Keyword Discovery or Keyword Tracker to find which words to use. You could also use an application like Market Samurai or Micro Niche Finder. My question is what is a good percentage of keywords to use - you don't want to over stuff it.

by adding the necessary information and met the purpose

If you mean how to associate the keywords to the backlinks, it's better to use your targeted keywords as the anchor text.
Social bookmark sites and web directories allow you to give tags on your links.

use keywords that is relevant in your website, try looking in google keyword tool to find the appropriate keyword for your website, another tip is try using a keyword with less competitors and lots of usage, you can see all of this information in google keyword finder..