Timeseries ids are in the table here: https://help.dynatrace.com/dynatrace-api/timeserie...
Host ids can be found in the URL param when you navigate in UI to that particular host details page.
Depends what metric you want to get use a timeserie Id from the table described here: https://help.dynatrace.com/dynatrace-api/timeserie...
Then to get entity Id - for instance host :
1. Go to Hosts page in UI
2. Select host that you want to use
3. Look at the page URL. There should be entity ID included in the parameters.
Better now ?