It's very important that your shop has the main domain already set.
Check out how to set a main domain.
In administration panel go to Configuration => Configure modules
Select Positioning module
Select Meta tags
The text appears in the site's header. The title appears in Google search results. This is the most important tag. Maximum width is 512 px.
Meta description tags, while not important to search engine rankings, are extremely important in gaining user click-through from SERPs. These short paragraphs are a webmaster’s opportunity to advertise content to searchers and to let them know exactly whether the given page contains the information they're looking for.
The meta description should employ the keywords intelligently, but also create a compelling description that a searcher will want to click. Direct relevance to the page and uniqueness between each page’s meta description is key. The description should optimally be between 150-160 characters.
Comma-separated words and phrases related to your shop.
Meta tags with shop's offers are generated automatically, eg. for a product - meta tags are based on product's name and description.
You can define a title's structure by adding keywords before or after a name marked as {NAME}.
You can also define mata tags individually for each offer.
Check out products documentation.
Check out categories documentation.
Check out manufacturers documentation.
Check out product groups documentation.
Check out information pages documentation.
Check out blog documentation.
Select Search engines verify
The most common method to verify the ownership to the search engines is based on a file.
An each search engine in its tools provides a file to download and upload in your shop in order to verify the ownership.
https://www.google.com/webmasters/tools/
http://www.bing.com/toolbox/webmaster/
https://webmaster.yandex.com/
You can find a meta tag in Google webmaster tools.
Select Google sitemaps
Links domain depends on the domain that is currently used in the administration panel.
http://www.shop.example.com/sitemap_en.xml
Select Edit robots.txt file
If you want to restore the original robots.txt file, Press Restore the original file
Select Redirect 404 links
Links to shop's pages, which were used can be read in Google webmaster tools
Redirect the old links 404 by using redirects 301 to a similar page with the current offer.
For example you have an old link http://www.shop.example.com/mobile-phone.html
/mobile-phone.html http://www.shop.example.com/mobile-phone-premium.html
/mobile-phone.html http://www.shop.example.com/category/phones
You can use *, to redirect the similar links eg.
*/phone http://www.shop.example.com/category/phones
Redirect all the links with a word phone to a category phones:
http://www.shop.example.com/mobile-phone.html
http://www.shop.example.com/category/mobile-phone.html
http://www.shop.example.com/my-phone
Redirect works if a site doesn't exist.
If you enter an URL of an existing site, it will redirect to the current site.
The higher an address is in a field, the higher redirect priority it has.
Select Generate SEO links