The proxy runs on port 8080 and only allows connections from localhost by default.
If you want to change the configuartion edit:
/var/snap/tinyproxy/current/tinyproxy.conf
and restart the service with:
sudo systemctl restart snap.tinyproxy.tinyproxy
To define filter rules for blocked urls you can edit:
/var/snap/tinyproxy/current/filter
and just add domain names or full url paths (you do not need http://) to that file and they will be blocked.
To make the new filters used you need to restart the proxy again with:
sudo systemctl restart snap.tinyproxy.tinyproxy
Logs are written to:
/var/snap/tinyproxy/current/tinyproxy.log