We change verbs to describe actions in the past (went, bought, did). The same thing occurs in the Russian language as well .
We make the past tense by replacing the infinitive ending -ть with:
1. -л (for masculine gender)
Он работал вчера – He worked yesterday.
2. -ла (for feminine)
Она работала вчера – She worked yesterday.
3. -ло ( for neutral)
Это хорошо работало – it worked good.
4. -ли (for plural: мы, вы, они)
Мы работали вместе – we worked together.
It is easy to remember for he (он) you need to use -л, for she (она) you need -ла.
Pay attention for I (я) and for singular you (ты) you may use both:
-л or -ла. It depends on who made this action in past: male or female.
Я думал – I thought (if I am a man)
Я думала – I thought (if I am a woman)