Last update: Jan 5, 2022 (verified with FileZilla 3.57.0)
You can download FileZilla from this site. Please install proper one for your environment (OS etc.).
Click the icon at upper-left corner of the window to enter site manager menu.
(If you register your private key at "SFTP" section in [Edit]->[Settings] menu or you register the key to Pageant, you can use Quickconnect. If this prior condition met, input sftp://ccfep.ims.ac.jp and RCCS user ID (three-letter-ID) in Host and username boxes, respectively.)
Click "New Site" in the site manager menu.
You can input connection target and other related information in this window.
(This dialog might be skipped if you already accessed ccfep.ims.ac.jp with PuTTY or other software which share host key information with PuTTY.)
You may see dialog like above upon first connection. You should check the fingerprint, it must match with one of the following list.
If fingerprint is OK, click checkbox (2) to skip verification from now on. Then, click OK to proceed.
(Although the text box title is password,) you need to input passphrase of private key. (If you have registered your key to Pageant, this step will be skipped.)
If everything works fine, you will see the file list of ccfep.ims.ac.jp in right pane. You can call this registered connection from down arrow at the upper-left (next to site manager button) from now on.