We use the particle に for saying that something is present at a certain location.
I am in the United States.
米国にいます。 beikoku ni imasu.
I have a car at home.
うちに車があります。 uti ni kuruma ga arimasu.
Note how あります is translated with to have in the sentence above.
When an event or action is happening at a particular place, we use the particle で instead of に.
I will buy rice at the shop.
お店で米を買います。 omise de kome wo kaimasu.
I drank a beverage at home.
うちで飲み物を飲みました。 uti de nomimono wo nomimasita.
Note the お in front of 店.
The お is an honorific prefix, showing respect to the person or object you are talking about.
There are several words that commonly go together with this prefix.
For example, it can also come in front of 水 to make お水.
Using お is polite, and in casual speech you would just say 水 and 店.