How to set up Opera for using proxy?
Proxy server settings are found in Tools > Preferences > Advanced > Network (Mac: Opera > Preferences > Advanced > Network). Click the “Proxy servers” button to open the proxy settings dialog. Tick the checkboxes for the protocols you want to use a proxy for and enter the proxy server hostname or IP address in the text field to the right of the protocol name (HTTP, HTTPS…). To the right of the protocols there is a box available for the port number.