I2C between Trinkets and Mega not working

thanks...i wanted to make something more than the others...but i didn't want to take 15 mins to explain how to hook everything up...part 1 is mostly for people who know I2C...but need to know how to link 5v and 3.3v devices together...part 2 will re-explain the I2C for arduino's and teach you it for the trinkets