To activate multiple meters at once, you can check the boxes next to individual meters, or the box at the top of the authorization to select all meters for an authorization, and then click on Collect Data. This will kick off a data collection job for all meters selected. See examples below.
Select just the meter(s) you need, and then Collect Data
Or, check the box at the top of the authorization, and Collect Data for all meters in an authorization.
The checkbox interface works the same for downloading the bills.csv file for multiple meters at once too. Check the box next to the meters desired with data, or all of them, and then click on "Download." This will create a zipped folder that will then download with all the bills.csv files.