BuddyPress.org

Hi,

this page is made of list elements and divs. To wrap them into columns, you have to adjust the CSS.
This can be done by child-theme, where you have to copy
bp-templates/bp-legacy/buddypress/members/register.php
to /your-child-theme/bp-legacy/buddypress/members/register.php

And CSS goes into /your-child/style.css

How to wrap <div> and <li> is out of the scope of this forum.