How do I differentiate between the articles le/la/les/un/une/des and when to use them?

These articles are used before a noun, the same way you would typically use the word "the" or "a" in English. Their use will depend on 2 characteristics of the noun they are used with: 1) Whether the thing/noun you are talking about is specific or unspecific. When discussing a specific object/person/place... you should use a definite article (le, las, les). For example, "I have an issue with my math exam paper and i need to talk to the math teacher." In this case the noun is definite -- the teacher is specific. When discussing an unspecific object/person/place... you should use an indefinite article (un, une, des.) For example, "I have an issue with my timetable and i need to talk to a teacher." This time, the noun is indefinite -- the teacher is unspecific, it could be any teacher2)Whether it is feminine, masculine, plural. For feminine nouns you would use : la, une. For masculine nouns you would use: le, un. When the noun is plural (no matter if it is feminine or masculine): les, des
(With the use of the whiteboard, I would provide a table to categorize the different articles)