Select the pod you want from the Kubernetes view in the Services tool window, then click on the Run Shell button. A new tab will open and a terminal will be attached to the running pod.

By default, the IDE runs /bin/bash as a shell. To run a different one, click Show Settings or open Settings/Preferences | Build, Execution, Deployment | Kubernetes and specify the shell that your pods use.

Note: You must have the Kubernetes plugin provided by JetBrains installed for this action to work.