Depending on the size of the comb you may be able to reattach the majority or at least a chunk of it back onto one or multiple top bars. This is preferably if you can because it won't disrupt any future comb building (cause other combs to be built askew). If it is a large piece I would recommend getting two zip ties and either piercing the comb about two inches down from the top and attaching it to the top bar or if it is a smaller piece attaching one or two zip ties around the whole piece of wax and the top bar. Any small pieces at the bottom of the hive with be broken down and reused by the hive. If you have some larger chunks of comb that cannot be attached I would recommend removing them because they will disrupt the straight building of comb on the surrounding top bars.
If you have any further questions about how to do this or any top bar beekeeping questions please feel free to reach out to our customer service line at 877-325-2221 or by email at firstname.lastname@example.org. Hope you have continued success with your bees!