First, you have to set up a discord channel where videos you are subscribed to will be posted. Go to channel's settings > integrations > webhooks and create a new webhook. Then copy its url.
Now we can link the application to the webhook and add some channels: Start the application by double clicking on it or run this command in a terminal :
python3 tui.py
In the app go to webhook, paste the copied url and press ok. Now you can add as much channels as you want. When you finished close tui.py and run main.py every time you want to refresh your subscriptions feed.