I used DC++ a long time ago.
Here's a tutorial for you:
First you have to connect to a hub which you can download from a public list.
After connecting you have to read the rules because I find the ops can kick you out easily.
If you find you are having problems connecting to a hub you might not be sharing enough.
The last time I check 10 GB of shared material was the minimum for most hubs. That's probably have increased in a few years.
If you're searching for files I suggest using MoGLO. This third party search engine will search all the hubs at once, though it may 10 minutes to run a complete search.
If you're downloading from somebody, I believe a passive connection cannot download from a passive connection. Meaning you better know how to use your firewall and router.
Personally I didn't like DC++. Too many overpowered ops and users who don't share properly. eMule is a better at sharing.