Zoom (LEARN) User Guide

How to set Join Before Host Setting
Initially, do the following (this is a one-time setting),
Go to settings and search for 
Allow participants to join before host in the search box.
Turn on the settling.
Check the
Participants can join check box.
Set the desired time by selecting it from the dropdown. It's recommended to keep the time either 
5 minutes before start time or 
10 minutes before start time. Do not set it to
anytime.
Check the settings below every time you schedule a meeting.
Scroll down until you find 
Options
Click 
Show 
See if the 
Allow participants to join check box is checked. If not, check it.
Adjust the time if needed.

How to Find the Host Key in Zoom
Login to zoom. Make sure the "Allow Zoom to start meeting with Host Key" setting is turned on by going to settings. It should be enabled and locked.
Select Profile Find the host key and note it down, or if you prefer, change it by clicking Edit.
After the Meeting is scheduled, share the host key with the person who needs to obtain the host role for your meeting.
Note: Make sure not to enable the "Waiting Room" option while creating the meeting.  
It is strongly recommended that the host key be changed frequently. to avert unforeseen events.
Also, make sure to enable "Join Before Host Setting" to use this feature on the meetings created under your account.

How to Use the Host Key to Claim Host Role in Zoom
Join the Zoom meeting. Click on Participants1, Check if you have the host role 2. If not, click on the Claim Host button 3.
Then enter the Host Key and click on Claim Host.
Check if you have the host role assigned.