I have done seo to my website and got into top 3 positions Now I want to do seo for another keyword what is the process. Should I follow the same as I have done for keyword1 should I need to build backlinks through the anchor text with that keyword please suggest
You have to follow the same process that you have done with the first keyword to make it rank on SERPS. It will so rank the same as the first one and if that keyword is lying at 50-60 position then it will be better to start with bookmarking first.
Depends on how relevant your secondary keyword is to the major one. If they are closely related you can promote the same page including the major keyword in the strategic places like titles and urls, and allocating some space in h tags for the secondary one, then just build some links with the secondary keyword in the anchor and it should take off. If the keywords are not closely related, I'd suggest creating a different page for the secondary keyword and promoting it just the way you did with the first one.
I agree with ingame but would like to add the importance of back links using the keyword as anchor text to the page you are optimizing for that keyword.
Yes you have to do the same things you had done for your main keyword. They will rank as well. And if they are related with your main keyword than you have to work even a bit less. Your secondary keyword will get weighted from your main keyword.
Will you explain the term secondry kwywords? please. Are you talking of those keywords which you did not incluede into your meta tags? Or those kwywords which you did not consider earlier. Anyway no new process...
Whatever you have done for you main keyword. do the same for your all keywords. these is no another way for secondary keyword