1. .Log in to your dashboard--> Design- -> Edit HTML

2. .Click on "Expand Widget Templates"


 3. Search "Ctrl+F"  the following cod:

<div class='art-content-layout'>
<div class='art-content-layout-row'>

4. Now add below code before the upper code

<b:section class='sidebar' id='magazine-left2' showaddelement='yes'>
<b:widget id='Text512' locked='false' title='Column 1' type='Text'/>
</b:section>

<b:section class='sidebar' id='magazine-right2' showaddelement='yes'>
<b:widget id='Text522' locked='false' title='Column 2' type='Text'/>
</b:section>

<b:section class='sidebar' id='magazine-center2' showaddelement='yes'>
<b:widget id='Text532' locked='false' title='Column 3' type='Text'/>
</b:section>

<div style="clear: both;"></div>

5. Add below code before ]]></b:skin> tag.

#magazine-left2 {
width: 33.33%;
float: left;
}
      #magazine-right2 {
width: 33.33%;
float: right;
}
      #magazine-center2 {
 width: 33.33%;
float: right;
}

6. Now save your template and you are done.