The creation of API keys doesn’t require any payment. Is it possible you purchased API points?
However, to answer your main question, you’ll probably want to use our data download tool. This tool will query the API for you and return the data you’re looking for. You’ll need to set up the tool, before you can use it.
Once you have everything set up, you can retrieve data in the “download” tab. To get data from all of the devices you want, you’ll have to get their sensor indexes. This number can be retrieved when you’re clicked on a sensor on the map. This guide will show you how to get sensor indexes.
Once you have the sensor indexes for the devices you want data from, input them in the “Sensor Indexes” field of the download tool separated by commas. As long as the sensors are “public,” you can leave the “Sensor Read Keys” field blank.
Then, all you have to do is choose what fields you want to query. A description of those fields can be found here: API History Fields Descriptions
Please let us know if you need further assistance or clarification.