If I can try explain best I can (ill try ). It basically comes down to trying to understand grammar.

The grammar structure in Japanese is usually: Subject -> Object -> Verb

Watashi wa(Me/I - Subject) -> Sushi (Sushi - Object) -> Tabemasu (Eat - Verb)

Japanese also has grammar particles, like in the above example 'wa'. There are varying grammar particles depending on the situation of the sentence such as 'de', 'ni' and 'wo/o'. These are used when connecting a sentence together and as far as I am aware are always in Hiregana. 'De' is used when describing going somewhere in a sentence, 'Ni' attaches onto a a destination, 'Wo/o' describes somthing specific within a sentence (like an object)

e.g Watashi wa Densha de Tokyo ni Ikimasu
(I went to Tokyo by Train)

e.g Neko ga misu o Nomimasu
(The Cat is drinking water)

So basically particles are used in sentences to help structure the grammar. By natural process of elimination and also by following the Subject -> Object -> Verb structure, it should hopefully be easier to understand. Throughout your classes you will learn more particles also.

Also, this can throw people off (it did with me at first) but with the structure of a sentence in Japanese, as long as the Subject and Object remain in the same place, the rest of the sentence can be thrown around.

e.g If we take the sentence 'I go to my Office by Train'. We can phrase it:

1) Watashi wa Densha de Kaisha ni Ikimasu

2) Watashi wa Kaisha ni Densha de Ikimasu

Same with any other sentence (unless there are other varient of sentences, im still a beginner myself ), so don't let it throw you off

Hope that helps