Quick tutorial:
1. Download
dslazy
http://blog.dev-scene.com/ratx/archives/1
2. Open your populous rom and select
'NDS unpack', wait till it's done.
3. Go to the folder
data/text/ and open the English folder, mark everything and select copy.
4. Now go back one folder and open the Japanese folder, select paste and select yes to overwrite everything.
Save the text file and go back to dslazy.
5. Select
'NDS Packer'
When it's done, select where to save it and there you goÂ
EDIT: Didn't notice I used the text file way on the rom I already copied the language folders onÂ
Will work now.