Please note: The following documentation was written for the original eMule client. There are different eMule forks / modifications out there, e.g. "eMule Plus". There have been problems at least with eMule Plus. For some reason they seem to have built in IP based filtering. Users with the IP addresses of the YF servers get a LOWID or are prevented from accessing the eMule service. I don't know why this is the case but I can only advice you to use the official version from http://www.emule-project.net/home/perl/general.cgi?l=1 or another P2P client.
Thanks to daibatzu for supplying the original documentation.
First, Download, Install and Start eMule - you can get it here
When you run eMule for the first time, a configuration wizard will start. It's not flexible enough, so just click through it, we change the wrong settings later. When done, click on "Options". Then highlight "Proxy" and adjust according to this example:
Note: If you intend to use OpenVPN mode, do not configure a proxy. It won't hurt a lot but it unnecessarily submits you to Your Freedom's number of concurrent streams restrictions.
Next, click on the tab "Connection". If you are a TotalFreedom user, configure the TCP and UDP port to be one of your assigned ports (make sure you add a server port forward in the Ports panel of Your Freedom as well, with both port numbers the same as in eMule, and localhost as the target host) -- this will get you a "high ID". Enable Kademlia as well. If you don't have TotalFreedom the port number does not matter and you will have a "low ID" no matter what you do.
Also, make sure you have the maximum connection setting right -- it should be below your Your Freedom profile's maximum! (Unless you use OpenVPN mode, in which case you can set it as high as you like.) Leave some headroom for server connections. For TotalFreedom users, 195 is a good figure. EnhancedFreedom users should use 95, and BasicFreedom users will have best results with 27. FreeFreedom users should use 7 or 8.
It also helps to be conservative with your bandwidth settings. You need not only take your Your Freedom limitations into account, but also your bandwidth for the tunnel connection. If you are behind a DSL link that will only give you 50kBytes/sec uplink speed it's best if you stay slightly below this figure, say 48. You should limit the bandwidth in the Your Freedom client as well, it improves transfers in the other direction if you do.
Well mostly. Kademlia will only work in OpenVPN mode (it works better with server port forwards but it will also work without, using a "buddy" to connect); the eMule client is silly enough not to use the proxy settings for connections to the Kademlia network (at least in version 0.48a). If it works without then it's not through Your Freedom!
Oh, and be careful which Your Freedom server you are using; some are not permitting the eDonkey2000 protocol.