Follow the instruction below on adding a Slack Workspace you are a member of to your Slack Mobile or Desktop App:
Open your Slack App from your Mobile or Desktop App:
From your Desktop App select the plus (+) sign on the left hand side of your app.
From your Mobile App on an iOS device swipe right until the Workspaces page is displayed.
From your Mobile App on an Android device swipe right and then select the icon in the top right to display the Workspace page.
Select the Add Workspaces option at the bottom of your Slack Workspace.
From your desktop app you will be taken to a web browser. Enter the Slack URL for the workspace you are trying to add and then select the Continue button. If you do not know the Slack URL see, How to Find the Workspace's Slack URL Address.
In your browser if you are not already logged into your ASURITE account you will be taken to the Sign in to Arizona State University screen. Select the Sign in with your ASURITE ID button and sign in using your ASURITE Username and Password. If you are already signed in skip to step 4.
Slack will connect to the Slack Workspace and then after a few minutes you should be redirected.
You should receive a prompt similar to the one below asking to open the Workspace in your Slack App, select Open Slack.app.