For Firewall/Appliance Setting the SSLVPN instruction, please click here to follow official instruction.
https://www.sonicwall.com/support/knowledge-base/170505401898786/

First you need ask the IT Administrator to get the following information:

  1. Link and IP address for SSLVPN access
    e.g. https://203.80.247.11  or  https://203.80.247.11/sslvpnLogin.html
  2. Username and Password
  3. Server Address
    e.g. 203.80.247.11:4433

Step 1: Search “Sonicwall” in AppStore

download and install it

Step 2: Open the Apps

Step 3: Accept the License Statement

Step 4: Add Connection

Step 5: Create a new connection

Step 6: Enter the connection name and server address

then click “Next”

Step 7: Enter the connection username & password then “Save”

Step 8: Click “Allow” to let apps create VPN connection on your iOS.

Step 9: Enter Pin or TouchID to confirm allow, then “Done”

Step 10: Just click “VPN” for connect and disconnect the VPN

Remark: After connected to the VPN, it will show “VPN” at top banner