Depending on what Tamagotchi you have, its different. ConneXion and Plus is going into time mode and pressing A and C at the same time until the word SET comes. Then, when you are ready to play again, set the time (and date, if needed) to the correct time/date. As for connections, you press A button and hold, then press B. It should say that the Tamagotchi is paused.
Also see
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What is the difference between a ConnECTion, ConneXion and ...