Yesterday's conjugation of the simple past gives a way to express the past. Harder than learning the verb forms though, is learning when to use it. The good news is that if you use the wrong past tense you will nearly always be understood, in the same way that a foreign person speaking English will often make mistakes but still be understood. The simple past is used to represent a single event, a point in the past, never for something that is ongoing.
Therefore 'tiré' can translate 'I threw', but never 'I was throwing' or 'I used to throw' which would be translated using the imperfect tense - more on that in future posts. However, 'I threw' is not necesarily translated as 'tiré'. 'I threw a ball every day' would also be translated using the imperfect tense because it refers to a repeating, ongoing event. Practise of reading and listening is the best way to learn when Spanish people would use each tense.
There are another couple of points which are important to note. Firstly the pronuncuation - it is important to stress the accented sylable, otherwise the words will be heard as the present tense. The stress in the simple past falls nearer to the end of the word in most cases.
Secondly, the first person plural ('tiramos' / 'we throw') is the same in the present and simple past tenses, so the context has to be relied on to indicate which is meant.