Visit Admin Panel-> Settings-> Setting-> UI/Theme Settings ->Edit.
Note:- when “single line” header is selected from the drop-down list it is going to show a single line header on the front end side as it is shown below in the image
Selecting two-line header style
Note:- when “single line” header is selected from the drop-down list it is going to show a single line header on the front end side as it is shown below in the image