When you don't know any foreign language, we allow you to use cucumis by giving you %p points every %d days (only when you log in and when you actually need them).
Si no sabe ninguna lengua extranjera, dejamos que usted utilice cucumis al darle %p puntos cada %d dÃas (sólo cuando comienza una sesión y realmente los requiere).
Remarks about the translation
I used the formal usted rather than the less formal tú. Instead of saying "when you don't know" I wrote "if you don't know" because it makes more sense in Spanish. "Dejamos" is literally "we allow/let" it could also be translated as "se deja", which would be impersonal, passive voice.