for the ACE editor for 757 and 727 go to you main fsx folder then look for a folder called captain sim open it and in side you will see 757 and 727 folders open one up say the 727 for example

in that folder you will need to open the variants folder and drop your repaint texture folder in there then go back to the 727 folder and you will see another folder called ACE this is were the ACE editor exe for the 727 open it and run the exe (ACE_727)

When the ACE editor is running look at the two tabs on the left and hit the add new then when the page has changed hit select variation tab and select your repaint
then at the bottom hit add  variation thats it simples

but don't forget to add a texture cfg in you repaint folder your best bet is to take one out of the main 727 folder in fsx