While in a call you may put the Lead on hold by following the steps below.

Call function buttons will appear in the upper right part when in a call. Below are the following buttons you can use.

To put the call on hold, click the Hold button, you will hear a beep and the hold button will turn red which means that you have successfully put the lead on hold.

To remove the lead on hold status, click the Hold button again, you will hear a beep and the hold button will turn back to white which means you have released the hold status.