Certain Seagate drives are supported by the Works With Chromebook program. Newer Seagate branded external drives come preformatted with the exFAT file system, which allows it to be used between Mac, Windows, and Chromebooks without reformatting the drive. This article addresses how to format the drive directly from your Chromebook. Chrome OS supports different file systems, see supported file systems supported by Chrome OS.
Note: Formatting a drive is a data destructive operation.