You should add the target="_blank" and rel="noopener noreferrer" in the anchor tag.
For example:
<a target="_blank" rel="noopener noreferrer" href="http://your_url_here.html">Link</a>
Adding rel="noopener noreferrer" is not mandatory, but it's a recommended security measure. More information can be found in the links below.
Source:
You can simply do that by setting target="_blank", w3schools has an example.
set the target attribute of your <a> element to "_tab"
EDIT: It works, however W3Schools says there is no such target attribute: http://www.w3schools.com/tags/att_a_target.asp
EDIT2: From what I've figured out from the comments. setting target to _blank will take you to a new tab or window (depending on your browser settings). Typing anything except one of the ones below will create a new tab group (I'm not sure how these work):
_blank Opens the linked document in a new window or tab
_self Opens the linked document in the same frame as it was clicked (this is default)
_parent Opens the linked document in the parent frame
_top Opens the linked document in the full body of the window
framename Opens the linked document in a named frame
It shouldn't be your call to decide whether the link should open in a new tab or a new window, since ultimately this choice should be done by the settings of the user's browser. Some people like tabs; some like new windows.
Using _blank will tell the browser to use a new tab/window, depending on the user's browser configuration and how they click on the link (e.g. middle click, Ctrl+click, or normal click).
Source: Stackoverflow.com