To create a conference call you need to be in a call. From there follow the instructions below.

• 1. Click
  2. Search for a contact or type in the number
  3. Click
  There is no limit to how many people you can invite to a meeting. Repeat the process to add more people.
• 1. Tap
  2. Search for a contact or type in the number
  3. Tap
  There is no limit to how many people you can invite to a meeting. Repeat the process to add more people.

There are more ways to invite participants to a call when you have created a conference, you can read more about it here.