The easiest way to manually copy your public key file is the following:
Open the Profile Settings page of the Settings dialog, or select Edit -> Settings, and click Open... next to the User Settings Folder field. The folder containing your user settings is opened. The folder contains a subfolder called UserKeys.
Double-click the UserKeys folder to open it. The folder containing your user keys is opened. Select the file that contains the public key that you want to copy to the remote host computer. Note that the public key has the file extension .pub. Be careful to you copy the file with the .pub extension, and not a similarly named file without a file extension (which would be your private key that you have to keep secure)!
Copy the file to the Windows clipboard by pressing Control+C on the keyboard, or by clicking the file icon with the right mouse button and selecting Copy from the shortcut menu.
Now connect to the remote host server and open a file transfer window, as described in Section File Transfer Window. Your home directory should contain a subdirectory named .ssh2. If you do not see the .ssh2 directory, check that you have the Show Hidden Files option selected on the View menu.
Enter the .ssh2 directory and copy the key file there from the clipboard: press Control+V on the keyboard, or click the right mouse button and select Paste from the shortcut menu.