Opteo is an official app in ChatGPT, so you don't need Developer mode or a custom connector. It works on any ChatGPT plan.
Go to chatgpt.com/plugins and search for Opteo, or open the Opteo app in ChatGPT directly.
Click +, then Connect.
ChatGPT opens Opteo in your browser. Sign in if you need to, then click Allow Access.
Opteo is now connected, and you can use it in your ChatGPT chats.
On a ChatGPT Business or Enterprise workspace, your admin may need to allow the Opteo app before you can find it.
To disconnect, see Disconnect or reconnect the Opteo MCP.