as far as i know, through two ways an addon is translated.
1. after the respective addon is installed then translated .xml file is overridden in
Appearance > language > import
selecting file
then override with English
this way you can install the translation of addon..
## how the translated xml file is made described below
in every addon you will see _data folder, there is phrases.xml
these phrases are translated manually...
i did this in notepad++ with the support of Google translator.
(say Turkish to English like the addon XenGenTr Ekstralar Sistemi).
then with translated xml file..
through the afore-mentioned procedure, you override the phrases.
PS: if you don't know html php, then don't do it yourself... there is some specific variables and everything related to the addon.. if u do some mistake, the addon will not function properly. translation recommended by experts.
2. if you don't have the translation of an addon, you can manually translate them in admin panel.
But i don't know php html language that much.. so i follow this procedure.
first, go to the add-on section, select the addon.
on the right side.. clicking on it, you will see phrases, public templates..
go there and change the phrase into ur desired language... again if u don't know html php don't do it carelessly..
(if u have overridden the translated. xml file... you will then see the color of the addon's phrases has become red, (from blue to red)
blue means original one, red means the phrase has changed... you can revert it too if u don't like the translation)
I had the translated xml file of XenGenTr ekstralar sistemi.. but i didn't like the translation... some were not translated properly.. so i did the rest by myself.
hope u get it..