Turn on Proxy in Settings → General → Proxy, and sign in to the site you want in a Proxy tab, or let it copy your login from Chrome (see Proxy accounts and logins).
In a thread, ask the agent to start recording. Then do the task yourself in the Proxy tab, something that only reads, such as opening your inbox or searching for a name. Ask the agent to stop recording and turn what you did into a capability.
Read the draft it shows you: the name, the inputs and what comes back. Ask for any changes, then have it saved. It's now a tool every agent can call; see Teaching Proxy a site for what it does under the hood.
Finally, put it to work. Ask the agent to run it and show the results as a table with a button on each row, either running another capability or opening the item in Proxy. That's a small tool of your own, built by doing the task once.