Bueno, es un poco largo el tema, quizás podrías empezar por aquí: https://espanol.lingolia.com/es/gramatica/preposiciones Cualquier duda puedes entrar en contacto conmigo. Saludos! Alejo. REF.: I'm a Spanish Teacher

You can start with this . A=To , En=In/on ,De=of. Examples: Voy A ir A la playa= I will go to the beach. In this case the first A is used before the verb IR, that means I'm going to go (voy A ir). It's used before a verb of something you will do at the momment or in the future. Here are more examples Voy A estudiar=I'm going to study ,Que le vas A comprar? =What will you buy for him/her,Voy A pescar=I'm going to fish. Now the second A of the first example (A la playa) = To the beach , in that case A is used to indicate a place to go.Examples: Voy A ir A la sala= I'm going to go to the living room, Ellos van A la escuela=They are going to the school, Todos van A el evento=Everyone goes to the event. Note: If the word is femenine then you use LA(The) before the word(La escuela), if it's masculine you use EL(El evento) when it's masculine you can use the article Al ( A el )it's a contraction and it's commonly used.(Todos van AL evento). The preposition EN is less complicated than A cause it's the same as IN in english or ON.Examples: El cuaderno esta EN la mesa=The notebook is on the table Delia esta EN su casa=Delia is in her house USA esta En America=USA is in America En que sentido...?=In what sense..? Note:To say in spanish if something is IN( inside ) we use DENTRO or ADENTRO , to say that something is ON ( over something) we use SOBRE or ENCIMA.Those words replace EN when it's necessary to specify. DE means OF (someone or something) examples: DE quien es la casa? = Whose house is this? ,DE que esta hecha la casa? =What is this house made of?,El libro es DE papel=The book is made of paper, Hoy es 4 de Julio =Today is 4th of July. If you have any question contact me.

Puedes encontrar las preposiciones y su uso en este link, espero te sirva, Saludos. http://www.practicaespanol.com/es/preposiciones/art/121/

Es un poco amplia la pregunta :/