The story repeats again and again :-D
Get it from your hosting provider.
But in general, this is a long question to discuss, and miniBB is not a project to answer the common questions you should know before... at least I have no possibility to answer such questions. If you can't drive, you call the taxi, and our taxi is our
paid support here.
Maybe some other users could answer you more.
You may check these threads as well:
Installing miniBB by newbies...B-A, BA Complete newbies/dummies thread, or What should you know before installing miniBB
