If you go through the HSTi user guide for your operating system, you should have setup your shared folder to share with 'Everyone'. If you have done this, then you won't be asked for a password when you try to connect to a share or PC.
If you find just a PC name and no folders in the setup wizard when you go to add your shares (Step 3) then simply click on the PC and it will ask you for a username and password. This is usually the same username and password you have setup on your PC. So if you enter a 'username' and 'password' when you first log onto your PC/Mac, then that is the username and password you would use when sharing with the stick.
Also, you need to have a password set on your account if you are not using the Everyone account to access your shares. This means, if you have no password to login to your PC/Mac, then you will need to either create a password for that account, or ensure that the 'Everyone' account is being used to share your folder.