Hlo Friends,
Mention which is the most important area to include your keywords?

For SEO purpose, Keywords should be included in:

Title
Content
**** tags
Headings (h1 tag)
Alt text
Anchor text etc.

Page Titles
Meta Descriptions
Subheadings
Content
Images
URLs
Link Anchor Text

Page title
Body text
Meta Description

The most important areas to include Keywords are:
Title.
Meta description (it is not ranking factor, but with the proper keyword, there is also proper answer to the search query in the search engine).
URL.
Content on your web (but do it naturally and understandable for your audience).
Anchor text (linking either internally and externally).

Website url
Website content
Meta description
Title of your website.

The seo title tag....