Prepositions

Prepositions of place can be used to show where something is located.  

We can find the prepositions in, on, at.  Next you are going to see a short explanation of their usage.

We use at to show a specific place or position.

For example:
Someone is at the door.
They are waiting at the bus stop.
I used to live at 51 Portland Street.

We use on to show position on a horizontal or vertical surface.

For example:
The cat sat on the mat.
The satellite dish is on the roof.

We also use on to show position on streets, roads, etc.

For example:
I used to live on Portland Street.

We use in to show that something is enclosed or surrounded.

For example:
The dog is in the garden.
She is in a taxi.
Put it in the box.

We also use in to show position within land-areas (towns, counties, states, countries, and continents).

For example:
I used to live in Nottingham

Here you can see some pictures that help you to see the positions of these prepositions:

In this video you will see a teacher explaining the rules for the use of prepositions, so check it out and enjoy it.

The following link can help you to clarify doubts. There you will see a short explanation about the use of prepositions of place and also some written exercises.

http://www.inglestotal.com/prepositions-of-place-on-in-at-preposiciones-de-lugar-en-ingles-on-in-at-lesson-9/