I can see three basic ways of doing this:
1) Filebased. In this scenario, you export the data from DB2 in some known format, say CSV, and the schema as a plan text .sql file. Then you have to fix the schema to match what is supported by MySQL and then import the data using, say, LOAD DATA INFILE, mysqlimport. You might have to massage the data a bit before importing it. You don't say what OS you run MySQL on, so I can't tell you exactly how to go ahead and do this.
2) ODBC or JDBC based. In this scenario, you use some tool that connects to databases using ODBC or JDBC. You would then connect to both MySQL and DB2 and move the data while being connect to the two of them, or even being connected to one at the time. This will probably not aid you in migrating the schema, but the data should be OK. If you have few tables and only simple data, this could be an option, assuming of course that you have an ODBC driver for DB2. An example of a tool that I have used for this, which should only be used for small amount of data and tables, but which works for testing purposes, is Excel or some other ODBC capable spreadsheet.
3) An integrated full-blown migration tool. There are things like this around, both commercial and open-source. This page on MySQL website shows you many such tools, both commercial and open source:
http://solutions.mysql.com/software/?c=migration
/Karlsson