You can add a Co-driver from the home page of the app.
Before you add a Co-driver to your device, both of you need to have a driver account under the same Carrier. Here are a couple articles to help get everyone signed up and accepted by the Carrier.
In the Current Load Out section of the BIT app home page, tap the plus sign to invite your co-driver. You will be able to choose from a list of all the drivers in your Carrier.
Type the first few letters of their name in the search field to quickly find the driver you're looking for.
Tap their name to select them.
Next, you will choose the settings for you and your Co-driver.
If you are sharing one phone or tablet to connect to the ELD adapter and record your logs, then select "Yes, we will share this device", and continue on with this article.
If you are going to use two devices, select "No" and continue to this article about Co-driving with separate devices.
Then select who will be driving first, and tap "OK".
Whoever was chosen to drive first will be shown as the Driver in the Current Load Out section. The Driver can tap the duty status icon to make changes, and any duty status changes or edits will be logged on the Driver's account.
You'll see new icons displayed for the Co-driver in the Current Load Out section. Their duty status icon is gray, because their account is not active in the app, and they can't change duty status.
Tap the icon with the two arrows to swap Driver and Co-driver.
Tap the X icon to remove the Co-driver.