For a simple two column layout, create a .row and add the appropriate number of .col-md-* columns. As this is a 12-column grid, each .col-md-* spans a number of those 12 columns, and should always add up to 12 for each row (or the number of columns in the parent).
Please read more for Bootstrap grid system here: https://getbootstrap.com/docs/5.0/layout/grid/
<div class="row">
<div class="col-md-6"> this is 1/2 columns </div>
<div class="col-md-6"> this is 1/2 columns </div>
</div>
<div class="row">
<div class="col-md-4"> this is 1/3 columns </div>
<div class="col-md-8"> this is 2/3 columns </div>
</div>
<div class="row">
<div class="col-md-3"> this is 1/4 columns </div>
<div class="col-md-9"> this is 3/4 columns </div>
</div>