DPA does not include disk space monitoring out of the box, but there are DMVs that can help us create a custom alert. The DMV is named dm_os_volume_stats and when it's joined to the sys.master_files table, we can see available bytes and total bytes for each database file. Aggregating that at the drive/mount point will allow a free space percent to be calculated for each drive.
To add this alert into DPA, create a custom alert of type Custom SQL Alert - Multiple Numeric Return and paste in the attached query. For thresholds, since we are calculating free space, use ascending values. For example, use 0 and 5 for critical (which means between 0 and 5% free space) and 5 and 10 for medium: