I just downloaded keypass and launched it. But it asked me to input master password. Well, I just used it and haven't created any password. How can I have the master password? Please see the image below.
Try unchecking the box that says "use master password and keyfile" and clicking cancel, or just click cancel.
You can then do file..new and create a new database file with a password, or do file..open and open an existing one. Also, a key file is optional. It's possible to have a master password without specifying/having a key file.