If your Confluence Admin granted you rights to use the Werewolf for Confluence app, you can find the relevant section in your profile menu.
Note that all your actions on behalf of another user are logged. The audit log is available for your Confluence Admin.
Navigate to Werewolf settings, select a user and push Login – now you are able to perform the actions in the system on behalf of the user you selected.
Don't forget to 'un-werewolf' when finished – just navigate to the profile picture and select the Un-Werewolf option in the drop-down menu.