je ne compre, nd pas quand on utiliser les articles différences, s'il vous plait tu m'aide

If you are referring to an unspecified quantitiy of something (in English one would sometimes use "some" in these cases), you use the article:

Je voudrais du thé, s'il vous plaît. -- I would like (some) tea, please.
Il boit de l'eau. -- He is drinking (some) water.

If you refer to a quantity (nothing being also a quantity in this case), you just use de:

Je voudrais une tasse de thé. -- I would like a cup of tea.
Il ne boit pas d'eau. -- He doesn't drink water.

It helps if you can ask specific, focused questions, otherwise it is difficult to answer without simply repeating what's been said in the lesson.

when you are talking about food & drinks, you will use them regularly on daily basis to express your activities like:

Qu'est ce que tu manges?

je mange de la viande.