Looks like whatever folder you placed the diablo miner code isn't in your CLASSPATH environment variable. (or you haven't set you CLASSPATH environment variable)
On Windows you set this with the system page on control manager. (years since I did it, sorry) on Linux
export CLASSPATH="$CLASSPATH:/wherever"
Which sets it for one terminal session.
Hope this helps
Thanks for help. But I'm realy new to it, could you please describe step by step what, where and when I need to do?) For example, should I replace word "wherever"? And should I use quotation marks ("")?