You can talk about having things with the word 有 (yǒu) - “to have”. Remember that you don’t need to conjugate (change) verbs in Chinese, so 有 is always 有 no matter whom you’re talking about.

The structure is simply:

[subject] 有 [object]
Let’s have a look at some example sentences. Notice that the nouns in the sentences have measure words before them: 个 (ge), 本 (běn) and 把 (bǎ).

Wǒ yǒu yī gè mèimei.
I have a younger sister.
Wǒ yǒu yī běn shū.
I have a book.
Tā yǒu yī bǎ qiāng!
He has a gun!
Hopefully you won’t ever have to use the last example sentence there.