Here's how:

1. Remove carbon filter from the coffee machine if present. Carbon filters are used on coffee machines to remove city water chlorine so it doesn't affect the taste of your coffee and because the sanitizing tablets are chlorine based we want to make sure any filters installed on the machine are removed so you can have the full concentration of the sanitizer to do its job.
2. Completely fill reservoir with clean water. Start with a full reservoir, you want to fill the reservoir higher than normal if possible to make sure you sanitize the entire reservoir.
3. Add 1 sanitizing tablet to reservoir, wait 10 minutes, stir. Although stirring isn't necessary it just makes sense to mix in any sanitizer that may have collected towards the bottom of the reservoir where the tablet is dissolving. Be careful not to stir to fast, you don't want to spill any and damage something you don't want bleached. Waiting 10 minutes allows time for the tablet to dissolve and for the sanitizer to do its job killing any bacteria that has grown in the reservoir, visible or not.
4. Brew 2 large cups (without a pod), wait 5 minutes. Make sure you don't have a coffee pod in the coffee machine, you want the sanitizer to come in contact with all parts of the machine. Waiting 5 minutes will give the sanitizer time to kill off the bacteria. 
5. Repeat step 4 until reservoir is at low level/empty. Brew as many large cups as it takes to empty the reservoir down to its low level indicator waiting 5 minutes in between every two cups. How many cups you brew will vary based on the size of the cup and how large your reservoir is.
6. Rinse reservoir thoroughly and fill with clean water. Any sanitizing solution left inside the reservoir should be carefully dumped down the drain, remember the sanitizer is chlorine based so you have the potential to bleach anything it comes in contact with. Thoroughly rinse the reservoir out with clean water so there is no sanitizer left in it. Typically two or three rinses is sufficient.
7. Repeat step 4 brewing 2 full reservoirs until empty. This is where you start with a full reservoir brewing 2 large cups and waiting 5 minutes repeating the process until 2 full reservoirs have been run through the machine. This will flush any residual sanitizer out of the machine.
8. Replace carbon filter, refill reservoir, enjoy fresh coffee. Once your flushes are completed you can replace any filters you had removed from step 1 and begin enjoying your bacteria free coffee machine.