The best RDBMS system to use as a beginner is probably going to be either MySQL or SQLite.
MySQL is an excellent database system and is capable of holding an extremely large amount of data. The data however is not stored in a movable file as you have described here.
SQLite is also an excellent database system and is capable of creating database files that you can move from one machine to another quite easily. The downside is that for a data set that large, you will likely have performance issues.
Based on the size of the file you mentioned, it sounds like what you have is a file with a whole bunch of SQL statements in it. Without seeing the contents of the file, it is extremely difficult to say which RDBMS it came from, but at the very least you should install MySQL and learn how to use it.