If you have not yet registered, you don't need to log in at all. When you enter the forum, pay no attention to the "Welcome guest" message. Just go straight to the part of the forum you want to see.
If you have registered, you should only have to log in with your user name and password the first time you revisit the forum - unless later on you log in from a new computer.
When you enter the forum at
www.mgsforum.org/smf/index.php and you see the "Welcome guest" message, put your user name in the user name box, your password in the password box, and then (important) leave the third box on its default "Forever" setting; then click the Log In button. When you finish looking at the forum, just exit the programme without clicking the Log Out button.
Then, next time you go to the forum, you won't need to log in at all.
If you have forgotten your password, when you put the wrong one in and you get the message that it is incorrect, there will be a small blue message at the bottom "Forgot your password?" Click on that, and you will be asked the question that you put into your Profile when you joined originally, that only you knew the answer to. Give the right answer, and your password will be emailed to you automatically.
If you have forgotten your user name, please get in touch with one of the moderators, and we'll sort it out.