To create terms & term set we should have privilege of a Contributor, a Group Manager, or a Term Store Administrator.
Simple steps to follow to create term set.
Step 1: Navigate to home page of root site and click on “site setting” of “Action Menu” and we get the site setting window.
Step 2: Here on the Site Settings page, in the Site Administration group, click on “Term store management”.
Step 3: Here in “Term store management tool” create a new group if required and right click on group, under which you want to create “new term set” as following image.