Any of our WHMCS addons and modules that support translations will contain a "lang" folder within them (for example: our PayPal Billing Agreements module contains a lang folder at /modules/gateways/lcwsoftpaypalbillingagreements/lang). These addons and modules will include a default "english.php" file that they will use. However you can create your own language file (for example: spanish.php for Spanish) by copying the "english.php" file and naming it appropriately (matching the language name that WHMCS itself would use), then translating the text in the new file accordingly. Do not change any of the variable or array item names from English, otherwise the new language file will not work as expected.
Once the new language file is in place, the applicable addon or module will use it automatically.
If you only need to change a English string and need the change to persist during upgrades in the future, you can create a folder named "overrides" inside the applicable "lang" folder (for example: this could be /modules/gateways/lcwsoftpaypalbillingagreements/lang/overrides). Copy the applicable language file into it (for example english.php and keep only the language strings that you will be changing. Then change them as desired. After doing so, they will be used automatically going forward.
