Closing manually
While an election is running, click Close election. You'll be asked to confirm — "Voting stops immediately and results are computed. This cannot be undone." Once confirmed, no further ballots can be cast, and results are calculated. You can close a running election at any time; there's no minimum voting window required.
Closing automatically
If you set an end time when scheduling the election, it closes itself the moment that time arrives — no need to be at your computer. See Scheduling: start/end times & timezones.
After closing
Results aren't published instantly to the second — you may briefly see "Results are being computed — refresh in a moment." Once ready, results are visible to you in the election's setup page, and you can choose to publish a public results link. See How results are tallied.
Closing is final: there's no reopening a closed election to accept more ballots.