When setting up a Sticky experiment you are asked to enter the amount of completes you are aiming to target. When the system receives that number of completes it will automatically close the experiment and start to process your results. The results will be ready shortly after.
If you are using your own panel and you do not reach the number of completes you originally anticipated, you can close it out on your own. If you hover over your experiment on your dashboard, you will see an option to select "Details". When you open "Details", you will see the option to "Generate Results Early". This will close the experiment and your results will begin to process.
If your experiment has already been closed out but you need to recruit more respondents, you can top off your participants using the same fielding method you originally used by clicking "Top Off Participants".