This is super easy
in your site, find the /language folder. Inside, you may see a folder named "overrides" - if not, create it. Inside of /language/overrides/, for each language you have installed on your site, create an override file:
en-GB.override.ini
fr-FR.override.ini
nl-NL.override.ini
Inside of this overrides file is where your translations live.
Let's say you created a cookie definition for Google Analytics and made the constants PLG_SYS_EPRIVACY_COOKIENAME_GA and PLG_SYS_EPRIVACY_COOKIEDESC_GA
Inside of each of these overrides files, you would translate the constant:
en-GB.override.ini:
PLG_SYS_EPRIVACY_COOKIENAME_GA="Google Analytics"
PLG_SYS_EPRIVACY_COOKIEDESC_GA="We use Google Analytics to better understand user traffic and traffic patterns on our site so we can sell more stuff."
fr-FR.override.ini:
PLG_SYS_EPRIVACY_COOKIENAME_GA="Google Analytics"
PLG_SYS_EPRIVACY_COOKIEDESC_GA="Nous utilisons Google Analytics pour mieux comprendre le trafic des utilisateurs et les modèles de trafic sur notre site afin que nous puissions vendre plus de choses."
And so on.
Easy, right?