In the field, upload or select your vanilla 1986 TrashMan .gba file.
Files for 1986-pokemon-emerald-u-trash-man - Internet Archive 1986 pokemon emerald utrashman rom free
To understand how a hack like this works, it is important to know that these files are . A fan creates a "patch" file (containing the changes). In the field, upload or select your vanilla 1986 TrashMan