A family of Microsoft word processing software products for creating web, email, and print documents.
Well, you were headed in the right direction, you just chose the wrong option :-)
Click in the Experience paragraph then go to Format> Borders & Shading. Instead of Horizontal Line choose a color if you wish, pick a weight, then click in the Preview area to apply the Border to the Bottom of the paragraph only.
If you just want to accept the default color & weight you can use the Borders button in the Paragraph group on the Home tab rather than going into the Borders & Shading dialog.