Using with Retroshare - PurpleI2P/i2pd GitHub Wiki

Retroshare is I2P capable.
Their configuration instructions for Java I2P. In order to do it for i2pd, you must create a new server tunnels in tunnels.conf like this

[Retroshare]  
type=server  
host=127.0.0.1  
port="port you wish to use"  
keys=retroshare.dat  

You can specify more options
Also keep SOCKS proxy enabled. It's enabled by default.

Start i2pd with this new tunnels, and get it's .b32.i2p address from http://127.0.0.1:7070/?page=i2p_tunnels. Now you are ready to create hidden profile for Retroshare. Mark it as hidden and enter your .b32.i2p and port you specified for tunnel.