How to enable user registration
If you want to run a multi-author website or blog, you need to allow user registration, so that each person can see their posts, edit and delete them as well as publish new posts. If you want to lock content from web spiders and website scrapers, you can show snippet of a post and show the full content to registered users. User registration is also useful when you want the users pay certain amount to view the content.
To enable user registration, you need to navigate through Settings>General and click the “Membership” check box and save. You can also set the role of the newly registered user by selecting the role below it.

Once you allow the registration, you can see a “Register” link below the login form.
You can use the Sidebar Login plugin to enable login from the main site in the sidebar.
I was providing the registration as a link on right sidebar. Sidebar Login plugin you mentioned is what I was looking for a longtime. I am not aware that such plugin really exists.
Thanks…thanks.