To talk about things being in places, use the word 在 (zài). This is actually a verb, so you don’t need to use any other words to talk about something being somewhere.

The structure is:

[something] 在 [place]
Have a look at some example:

Wǒ zài zhèlǐ.
I am here.
Nǐ zài nàlǐ.
You are there.
Shànghǎi zài Zhōngguó.
Shanghai is in China.
Māo zài shāfā shàng.
The cat is on the sofa.
Notice how English uses the verb “to be” where Chinese uses 在. English also uses prepositions - “to be in” - whereas Chinese often just uses 在.