I cannot connect to the WFC because it needs the ip adress and the connection fails

Click start type cmd press enter you will be in DOS mode
type in ipconfigpress enter you will see all of your internet connection details type in your default gateway ip adress into your internet search should read something like 10.0.0.138


Your IP Address should be thought more as your computer's phone number than it's address, if you have multiple connections, you have multiple IPs if you dont have a connection, you dont have an IP.

Without further delay If you need your computers IP address:
This will work in almost every case, it simply requests the website's server to tell you what your IP is. http://whatismyipaddress.com/
I have included a link to make things easier.

If you are in a network and need your computers local address.
Hold the windows button (looks like the windows banner, usually between left ctrl and left alt) and press 'R'.

A box will display, and type in "cmd.exe" and hit enter.
The 'command prompt' will display, a black screen with white lettering.
Simply type in ipconfig. This gives information on all your internet connections.

Look for the line "IPv4 Address".
If you need to find the IP of a current connection you can type (from the command prompt) "netstat".

This will give you all your current connections.
To identify a specific one, the easiest way is to run it before you establish the connection then again afterwards.
Change IP Addresses

Your IP address is a series of numbers that identify your specific computer on the Internet.
If, for some reason, you want to change your IP address, you can do so without going into the command prompt.Click "Start," "Control Panel," "Network and Internet" and "Network and Sharing Center."

Click "Change adapter settings."
Right-click the network you want to change and click "Properties."

Click the "Networking" tab.

Put a check either next to Internet Protocol Version 6 (TCP/IPv6) or Internet Protocol Version 4 (TCP/IPv4) and click "Properties."

Click the radio button next to Obtain an IP Address Automatically if you want Windows to assign one, or click "Use the following IP address" to manually change it.

Enter the requested information and click "OK."