To use ODBC to connect to an IBM DB2 UDB database like the one used by Accpac you need to:
1) Install the IBM DB2 UDB client on the client system
2) Install unixODBC and setup the odbc.ini & odbcinit.ini like in the example files
3) Login as the db2inst1 user on the client system and run db2

While inside the db2 shell you need to connect your client to the server like so
CATALOG TCPIP NODE sample REMOTE 192.168.0.77 SERVER 50000
CATALOG DATABASE sample AT NODE sample

Replace the IP address with the server name or IP that your IBM DB2 UDB server is running on.
If you want to use a name for the server make sure that your /etc/hosts file or you DNS server is able to resolve that IP address.

This command will show you the node information.
LIST NODE DIRECTORY

If you make a mistake you can remove the node like so.
UNCATALOG DATABASE sample
UNCATALOG NODE sample


IBM DB2 UDB user accounts and passwords are taken from the system it self. 
Use standard Linux commands adduser, passwd to alter if you need to.
If you are just testing using the sample data then you should not need to.