I’ve been able to make the Visibility section required by adding Required to the end of the input type field.

<label for="bp_simple_post_visibility_public">
                        <input type="radio" name="bp_simple_post_visibility" id="bp_simple_post_visibility_public"
                               value="public" required> <?php _e( 'Public', 'bp-simple-front-end-post' ); ?>
                    </label>
					
                    <label for="bp_simple_post_visibility_private">
                        <input type="radio" name="bp_simple_post_visibility" id="bp_simple_post_visibility_private"
                               value="private" required> <?php _e( 'Private', 'bp-simple-front-end-post' ); ?>
                    </label>

I’d like to make the Category section Required as well.

Can someone please point me in the right direction?

Thanks in advance.