Hi, Alex, When you purchase the paid version you get all the indicators and cBot as separate downloads, you can find each of these downloads in your ClickAlgo Account downloads.
Make sure you unzip the file and save it in a folder, to install double click on the extracted file.
Make sure you are using the latest version of cTrader v4.2 and above.
Read the user guide on how to get started.
I just added an indicator instance on cTrader 4.2.22 and it works fine.
If you are still having issues, can you provide the version of cTrader you are using and the exact steps you are following to install an indcator?