how can I use "get through"?

Get through normally means to undergo a difficult process with some degree of success. Success doesn't have to be complete. Example: The house got through the hurricane, although we had to replace a bunch of windows that got broken and doors that got blown away.

In Britain (I don't know about elsewhere) we also use 'get through' informally or conversationally to mean 'establish communication' or 'successfully convey a message'.

I tried calling my cousin on the phone but I couldn't get through [to him].

Last night I asked the hotel receptionist to make sure my breakfast was ready at 7 AM but evidently the message didn't get through to the kitchen.

(Angry boss, to junior employee): You have been found smoking in the office building twice now. The rules forbid smoking. if you are caught again you will be fired. Am I getting through to you?

He awoke and smelled smoke. He could hear crackling and it finally got through to him that the house was on fire.

May there are other meanings, for instance just to get done with: When you get through with it, turn it off

'Through' to mean 'finished' is almost exclusively North American, and not very common in British English.

Aha