In POL, select your account, then go to Settings.

At the top is where you put in your POL ID (ex: ABCD1234, should always be this format I believe,) then toggle the line below to "Save", then one line below is where you enter your POL PW. At the very bottom of the settings screen, enter in your SE ID (this is the same as your login here on the website) and toggle whether you use a One Time Pass or not. Make sure to save the settings.

If done correctly, when you try to login to the account, you should be asked for your SE PW (same as the one you use here,) and One-Time Password if you turned it on in Settings.

Everything is case-sensitive.

If you've forgotten your POL password, then you can login to your Account Management page here (link on main POL frontpage in top-right corner,) and change the POL password there.