Ok, I will use several VARIABLES to point where you should change the code to customize it for any league.
Check the bare-bone scheme on [url=https://fumbbl.com/FUMBBL.php?page=notes]https://fumbbl.com/FUMBBL.php?page=notes[/url], so it's more easy to understand what every change will affect.

GROUP_NAME: the name of the group/league
HOME_BLOCK_IMG: url of the toggle image for "home" tab
SCORE_BLOCK_IMG: url of the toggle image for "standings" external link
STANDINGS_URL: the url of the "standings"
HOF_BLOCK_IMG: url of the toggle image for "hall of fame" tab
IRC_CHANNEL_NAME: name of the irc channel of the group/league, if any
FORUM_THREAD_SEASON_URL: url of the forum thread for the current season, if any
LEAGUE_MOTTO: league motto, if any
OVERVIEW_CONTENT: write an overview of the group/league here
RULES_CONTENT: write the group/league rules here
AWARDS_CONTENT: write the group/league trophies here
DYK_IMG: url of the image to cycle through "Did you know?", 40x30 suggested size
DYK_1_CONTENT, DYK_2_CONTENT, DYK_3_CONTENT: content for DYKs
FORUM_THREAD_URL: url of the forum thread for the group/league, if any
GROUP_LEAGUE1_IMG, GROUP_LEAGUE2_IMG: url of the image to open past winners for a couple trophies
LEAGUE1, LEAGUE2: placeholder for two conference (?) in the league
TEAM_IMG: url of the logo winner team
TEAM_URL: url of the winner team
TEAM_NAME: name of winner team
COACH_URL: url of the winner team's coach
COACH_NAME: name of the winner team's coach