We haven't talked about places or times yet, but if you do an action at a time, you must attach the particle "에" to the word indicating the time.
"에" is also attached to a word to indicate that it is a place in the sentence. I want to write more about what "에" does, but at this point, it would only confuse you. For now, it is sufficient to know that "에" is used to indicate a place in a sentence.
Again, it is hard to translate these particles into English, but, "에" plays the role of the underlined words in the following sentences:
1) I went at 3pm2) I went to the park
Sentences with a place/time can also have an object in them. For example:
3) I ate hamburgers at 3pm
If I were to write those same sentence using Korean structure and particles, they would look like this:
1) I는 3pm에 went
2) I는 park에 went
3) I는 hamburgers을 3pm에 ate
In these cases, "at 3pm" or "to the park" act as adverbs (a word that tells you when, where, how, how much). There is no set place for an adverb within a sentence, and it can generally be placed anywhere (except the end). Adverbs will be discussed at length in Lesson 8.
Again, the purpose of this first part of Lesson 1 was to familiarize yourself with the different Korean particles and sentence structure. This knowledge will act as your base for upcoming lessons when you will apply yourself to make actual sentences with verbs/adjectives in Korean. While you will have to wait a little bit to create those types of sentences, we can now talk about creating actual Korean sentences with the word "to be."