youd have to import the invite.sql to your mysql, that step is fairly easy, you open up your administrator tool of mysql, and there should be an option of importing *.sql files.
This would create the database you need for invite.
About the ODBC connection between alcobot and mysql, do as followed...
start menu / run / odbcad32 "push enter"
choose the system DSN window, then Add... and select the ODBC driver "MYSQL ODBC DRIVER 5.1"
after that you input the info for your mysql Database, IP address, username / password.
Remeber to set the same Datasource Name as you have in your config settings of alcobot.
btw this invite script is only for the /msg _BOT_ !invite username pass feature when connected to IRC. You could use the internal one, the one for ioftpd only "site invite nick" this way a connection to any DB is not needed. Theres info about how you install the siteInvite.tcl in the readme.txt
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