Putting 2 contentarea side-by-side

Hi, I am new on Episerver. This is my 1st project. I may be asking a very simple question.

I am puttting 2 content areas side-by-side.

<div class="row">
@Html.PropertyFor(x => x.CurrentPage.LeftContentArea,
new{CssClass = "col"})
<div class="w-100 d-sm-none">&nbsp;</div>
@Html.PropertyFor(x => x.CurrentPage.RecentlyUpdateContentArea,
new{CssClass = "col"})
</div>

In CMS edit mode, they go on-and-on downward. Is there any render setting I need to put in?

Thanks.