Insert borders to a single column

There are several ways to border only one column. The question that makes the most difference is "Does the text from the bordered column have to be continuous into the next unbordered column?"

If the answer is no -- if the two columns are unrelated -- then you can use a text box or a table to contain the bordered text.

If the answer is yes, you can use text borders around the paragraphs in one column; you might need a column break at the beginning of the paragraph after that, to keep it in a separate column. Or you could use two text boxes, one with a border and the other without a border, and link them together so that any text that overflows the first box will go into the second one.

Finally, you could just type the text in the two-column layout, and then insert a rectangle shape (set its text wrapping to In Front of Text) with a border but no fill to cover one column. This is best done after all editing of the document is completed, to avoid the possibility of the shape being pushed out of place or needing to be enlarged or reduced to fit other edits.