What “Did” means
Did before a verb marks the past: "mi did go a town" means "I went to town". The verb itself never changes form. Did also works before adjectives for a past state ("mi did sick", I was sick) and stacks with other markers.
Examples
Mi did go a town yesterday
I went to town yesterday
Mi did sick las week
I was sick last week
Wi did a dance whole night
We were dancing all night
How to use it
Everyday and very common. Combinations to know: "did a" (was -ing), "did a go" (was going to), "did done" (had already).
Where usage varies
Often the past is left unmarked when context or a time word makes it clear ("im come jus now"). "Ben" does the same job as "did".