The smoke alarm does not have a reset button so there is no button to press. Fanning out the smoke alarm is all that is needed. If the smoke alarm quits making noise and goes back to the normal-green-light-is-flashing, the smoke alarm is ready to detect smoke again.
Testing the Smoke Alarm to Make Sure
Many brands of smoke alarms don't use a flashing light to indicate that everything is normal. In that case, another test can be used.
As a second confirmation that the smoke alarm is normal, the test button on the smoke alarm can be used. It really doesn't show whether the smoke alarm will detect smoke, but pressing it will show you if the battery is OK, the electronics inside the smoke alarm are OK, and the loud horn is OK. If pressing that test button causes the smoke alarm to sound off, then most of the alarm is probably normal.
If you regularly test the smoke alarm using the button, you can get used to seeing how it looks when everything is normal.
Look at the smoke detector before pressing the button. See if there are any lights lit or if they flash. What you see before testing is probably normal.
Press the button to sound the alarm. See what lights are lit. That gives you an idea of what lights are lit when there's smoke.
Let go of the button and wait for the sound to stop. Within a couple of minutes, the only lights lit should be the ones that were lit before testing the smoke alarm.
By testing the smoke alarm this way on a regular basis, you get an idea of what happens when it detects smoke. Be aware though, this isn't really a test of the smoke alarm's ability to detect smoke. You have to use smoke to determine that. Artificial smoke that comes in an aerosol can, like the professional fire alarm testers use, is recommended.