In warmer climates (i.e California), meter lids look something like this:
If your lid looks like the one above, then you can use the tool that came with your Flume device to open your meter lid. Please watch this short video for a quick demonstration.
In colder weather areas (i.e. Ohio Valley, Washington DC, Denver), most meter lids look like this:
The lids above are a little trickier to get open. For these lids, you must loosen the 5-sided nut before you can open the lid. You can use a crescent wrench for this task, however if you have a meter box key, it will make your life a lot easier!