The .broadPeak format is not a currently supported file format in IGB, however it can easily be converted to the more common .bed format, which is supported.
To convert the file to a bed file, limit the data to the first 6 columns. To do this on the command line use:
$cut –f1-6 FILE.narrowPeak > NEWFILE.bed
Optionally, you can replace the score field (column 5) with any one of the latter fields (columns 7-9 from broad peak format) to make that value appear as the score.
For more information about bed format: https://genome.ucsc.edu/FAQ/FAQformat.html#format1
For more information about broad peak format: http://genome.ucsc.edu/FAQ/FAQformat.html#format12
These file formats (both broadPeak and narrowPeak) have been recently requested by users, and we are preparing to add support for them in the near future.
We have a pending request to support these two formats without the need for manipulating files, and so now probably would be a good time to move ahead with implementing this. When it's ready, we'll post back here to let you know.