Assuming you mean how to say "I had lunch" or something similar, you could say:
J'ai pris le déjeuner
J'ai déjeuné
These aren't the only ways, however.
For other viewpoints (he had lunch, you had lunch, etc) you would change only "j'ai", replacing it with:
You (informal and singular): Tu as
He/She: Il or Elle a
We: Nous avons
You (formal and/or plural): Vous avez
They: Ils (males or a mixed group) or Elles (females only) ont
Pack lunch in French is: panier repas
le déjeuner
French lunch breaks are one hour long.
dejeuner
The phrase "after we eat lunch" directly translated to French is "après nous déjeunons"
French bread, yourself
Lunch is properly called "le déjeuner" (masculine noun) in French. That can be confusing as the breakfast is "le petit déjeuner" (literally the small lunch).
French baguettes with a side of French fries
dejéuner
déjeuner
Coffee
Food!