Translating WPtouch Pro can be done easily using a translation tool such as Poedit.
Translation may also be used to edit WPtouch's default text where other options are not available. For example, you may change the default text shown on the switch by creating a new translation file by selecting the .pot file in the /lang folder. By editing the text of the switch and saving the new .mo file to your active child theme, the switch link or any strings you edit/translate will display your edits instead of the default text.
In a translation tool such as Poedit, select "New catalog from POT file…" from the "File" menu.
In the Poedit dialog box, navigate to the plugin folder on your computer. Inside, navigate to the /lang/ folder.
Select the wptouch-pro.pot file.
Still in the Poedit dialog box, select where you want to save your new, translated file. Two files will be saved in the location you specify: a .po and a .mo file.
Proceed to edit the strings you want to change and save your work.
Rename the .mo file in the format wptouch-pro-YOUR-NAME.mo, where YOUR-NAME can be whatever you like. Make sure that the filename starts with "wptouch-pro-" for it to be recognized in WordPress. Also, do not use the default filenames. Example, wptouch-pro-es_ES.mo, as WPtouch Pro will automatically overwrite it with its own.
Connect to your server via FTP and upload only the .mo file to:
The /wp-content/wptouch-data/lang directory if you have a single WordPress installation, or
The /wp-content/wptouch-data/YOURSUBSITEID/lang/ directory if you have a WordPress network installation.
Go to WPtouch > Settings > General > Language and for "Theme Language" select the new translation that you uploaded.
Clear all caches before refreshing your website. You should see the changes take effect immediately.