Welcome to the forums, @uzair_naqash.
How to do seo for arabic websites?
The same way you would for any other website. The principles are the same, no matter what the language. I’d recommend Google’s “Search Engine Optimization Starter Guide” as the best place to start.
That seems an odd thing to ask. Yes, you can add Arabic words or phrases in an English article (making sure you mark the change of language in the HTML), but it’s unlikely to do you any good for SEO purposes. Search engines try to return the most useful results for the person searching. If I search for a word in English, it’s unlikely to be of much help to me to offer me results where that word simply appears in a page of Arabic, Japanese, or any other language I don’t speak. Search engines will look at the page as a whole. Much better to write in one language for your target audience, rather than trying strange tricks to insert keywords.