Bedrock quick answer: Add unstablesmp.net as the address and set the port to 19132.
- Open Minecraft Bedrock.
- Open the Servers tab.
- Add a server.
- Set the server address to unstablesmp.net.
- Set the port to 19132.
- Join Unstable SMP.
On Bedrock, the address and port are separate fields. The address is unstablesmp.net; the port is 19132.