The first step you need to take when learning how to open SEA files format is to try and understand what exactly the file is and which program can be utilized to open it. Over the last two decades there have been hundreds of different file types introduced, not all of which are familiar or common place. Of course certain formats such as Doc and PDF are known and used by the bulk of computer owners but others we may only come across on odd occasions.
A self-extracting compressed Macintosh archive file employs The SEA extension. The program that utilizes the SEA file extension is used to compress and build an archive for the Compact Pro, Disk Doubler, and the Stufflit formats, where the latter is the most commonly used.
With lots of software on the internet you should be able to easily open any kind of common file format. If a file format is proprietary you may need a particular program in order to run it. Often programs will let you associate the files that they can open with them automatically as part of the set up and the first time they are run.