Is Bitcoin Core running? You need to run that too.
How to know that
Did you download, install and run Bitcoin Core? It is a completely separate application from Armory. You would (should!) know if you downloaded and installed it!

If you haven't already, you can download Bitcoin Core from here:
https://bitcoincore.org/For Armory to work properly, you will need Bitcoin Core installed, running and FULLY synced. NOTE: this will mean that you will need to wait for it to fully sync the ~250 gigs of blockchain data.
Thank you very much, now I am downloading. And its size is very huge

. May it take about 2-3 days to complete the download.
Is it possible to bitcoin core from a selected date range like from 2018 and up to? It is downloading from a starting point of transaction.