Open your web browser and navigate to the PuTTY client download website here:
Click on "putty.exe" to download the PuTTY client to your download folder.
Open your download folder and double-click putty.exe:
Windows will pop up the following dialog to ask you whether you trust the application you just downloaded from the PuTTY website, click Run:
The main window of the PuTTY client will open and show a dialog to configure a new session upon first start:
Use "Saved Sessions" to name this session for later reference, type the name of the computer you want to connect to into the field "Host Name (or IP address)" (login.physik.fu-berlin.de in this case), click Save:
In the left hand side of the PuTTY window, click Translation below the item Window and make sure Remote character set is set to UTF-8, then click Open to make a connection:
You will be asked whether you trust the remote host, click Yes. This dialog will be shown upon the first connection only:
A terminal will open and ask for your username and password, your login should complete successfully: