Learn French: Nous venons de découvrir cet article dans le journal. - We just discovered this article in the newspaper.

You are right that venir usually means "to come". However, when you use venir followed by de and an infinitive verb (the basic, unconjugated form, like découvrir), it creates the recent past. This tells us someone "just" did something. So, nous venons de découvrir means "we just discovered".

Why do we use cet before article instead of ce?

For masculine singular nouns, the word for "this" is usually ce. But because article starts with a vowel, we use cet to make it easier to pronounce. The added "t" stops the vowel sound of ce from crashing into the starting vowel of article.

Would the de in venons de découvrir ever change to des or du?

No, the de in the venir de structure never changes to match a plural or masculine word. It is a fixed part of the expression. It will only ever change to d' if the verb immediately after it starts with a vowel (for example, venir d'acheter).

Why use dans le journal instead of au journal?