Use of nais i

I have reached lesson 12 for south wales but the “nais i” “nais di” etc. for the past tense is baffling me because I can’t find it written down anywhere, I am obeying the ethos of SSIW but the way I learn I like to see things written down at least once, and I have not found this in an dictionary or grammar book

Croeso (welcome) and llongyfarchiadau (congratulations) for coming so far and learning in the SSiW-way.
What you’re looking for is the past tense of " gwneud" = to do. It is written: "nes i “, “nest ti”, or , more formal: “gwnes i, gwnest ti” or " wnes i, wnest ti”, but in speech you’ll always hear "nes i, nest ti ".