The easiest way is to use built-in Webex features such as chat or Q&A. These are not enabled for every event so you may have to explore the Webex interface to find the appropriate option.
Enter your question in the Q&A panel.
In older versions:
In newer versions:
Q&A is in upper right corner for older versions
For newer versions, click on the button with 3-dots to reveal the Q&A menu
On mobile, go to the upper right of your screen.
Depending on version, look for the chat icon:
Click/tap on it, select the host or operator, and send your message.
Chat is in upper right corner for older versions
Chat is along bottom for newer versions