Prepositions express spatial or temporal relations, in Cainye "prepositions" are only really those considered to do the former, temporal relations are one of the jobs of the much more versatile adverbs. Some verbs have some necessary spatial relations in them, and in those cases prepositions are optional; the following verb ngât means "enter, go into", but the optional nin "into" is used to illustrate.

Xèyân sàng det là de ngât là nin cánbân
"I just started walking into the store."

Xèyân hí zâi héingi cánbân
"I am currently inside the store."

Zâi is a special "spatial copula", when the object has a preposition.

Xèyân zâi héingi xèyân ngéi
"I'm inside my home."

"Prepositions", in another analysis, are basically just adverbial phrases that can contain a noun phrase and sometimes a verb phrase, and modifies the main verb. The prepositional phrase is made up of the preposition, then the particle de. This is very common in Cainye and neccessary to understand. see below:

Xèyân xam yóngyòng de yīng yíncéin kù nin ngéi
"I drove home on the highway yesterday."

Multiple prepositional phrases are usually not strung together like PRE...de PRE...de, but the secondary ones are put in the object position, or before the object. Adverbs can go before or after a prepositional phrase.

Adverbs, and non-spatial or temporal prepositions can be put in the prepositional phrase construction, like below with ma "about, over".

Xèyân ma qángam lèngûnsì de gēu là ngêim
"I argued with my mother over the dishes."