@Builder,
Wikileak does not need to be running tor only you and you can hook up a ssl connection by way of tor network to wikileak and no one along the line can know what you are talking to them about or where you happen to be.
Now you run the software and it created a network/tunnel of three nodes, the first node know your isp address but not the content of your information or where it is bound for other then the address of the second node.
Oh your isp does not know the content of the information either or where it is bound for other then to the first node of the network.
The second node just know that it was handed the information from the first node and the exit node address, the exit node know the content of the information as it is the node that decryped the information and place in in the clear on the internet going to wikileak website for example but it does not know where the information came from and it can not be trace back to you over the internet.
Now if you do not wish to have the information in the clear at any point you just set up a ssl connection with wikileak website over your tor network before sending whatever information you wish to send them.
Oh the information flow is of course both ways and you hardly know you are using the system instead of just the open internet except for it being slower due to the overhead of the encrypting and the bouncing of your traffic over a large part of the world.
Beside security you can tell tor what country you wish the exit node to be in and by doing so bypass any country only limits.
For example the BBC had content that is not available to anyone with an out of england isp address so by setting the exit node in the UK you can sit in the US and get that content with no problem.
Then there is the darknet capability of this software but that is beyond what I am sure you are interest in at the moment.