Structured markup is data added to a web page that helps Google and other search engines understand what a particular piece of information is or does; to determine whether it is an article or an address for example.
There are different types of structured data; a popular one is named Schema (see schema.org).
You can add structured data directly through Google's Structured Data Markup Helper.
Below is the step-by-step tutorial to help you use Structured Data Markup Helper.
Step # 1
There are many data types on the website tag like movies, events, articles, restaurant etc. Click on the type of data your website is offering. I click on the Article as my data type. If you are not able to find your relevant type in the section then check the complete list on schema.Then enter the URL or HTML source page of your website and click on Start Tagging.
Step # 2
After that, a new page will open. You will see various elements of the tool page in front of you. The visual presentation of the URL is on the left side and the structured data information is on the right side.
Now tag data from the content of your webpage.Select different elements. Once you do this, the selected elements will be added to My Data items located on your right sidebar.
You can also use clear tag if you have accidentally selected the wrong element. Select all my data items on the website and just tag it into right field, If you want to add any missing tag in it which you cant find then use add missing tags for that.
Step # 3
Once you are done tagging elements of your data, click create HTML. This will create the HTML code for your micro data. The coding can be seen in the right side of your page. Whatever micro data has been coded is shown as highlighted text so that you can make changes if required.
Your code is ready now. You can simply copy paste the HTML file or click on Download button to get it on your device to update your site.
Finally, after implementing it on your site you can have a preview by using Google's testing tool to make sure there is no bug in it. You can find this Structured Data Testing Tool in your Webmaster Tools. Simply enter the URL of any article in the bar and click Preview. Make sure everything on your site looks perfect.
I hope this article helped you in overcoming issues needed to build a Schema-friendly website through webmaster.