The most commonly used particle in conjunction with time is the に-particle.
Up until now, you have used this particle to show presence at or movement towards a destination.
In addition to that usage, it also means at when following a time.
I bought the tickets at eight o'clock.
私は八時にチケットを買いました。 watasi ha hatizi ni tiketto wo kaimasita.
She went to New York in February.
彼女は二月にニューヨークに行きました。 kanozyo ha nigatu ni nyuu yooku ni ikimasita.
Would you like to do something Friday?
金曜日に何かしませんか？ kinyoubi ni nanika simasen ka?
Note that though に is used with the time expressions including hours, weekdays and months.
There are other cases in which they are not used together with a time expression, as in the sentences below which you have learned earlier.