DNSpresso is an exploit that takes advantage of a vulnerability in the Wii U's DNS response parsing. This should be used if BrowserHax is not possible for whatever reason.
Extract the contents of the newly downloaded Tiramisu .zip file to your SD card. You should now have a wiiu folder on the root.
Extract the contents of the PayloadFromRPX .zip file to the root of your SD card and rename the file to launch.rpx .
Your SD cards root should now look like this:
(root)
wiiu
launch.rpx
Section II: Running the Exploit
Insert your SD card into your Wii U and power it on.
Open Settings > Internet > Connections and setup a new connection.
Once created, click on your new connection and select Change Settings > DNS and set it to Don't Auto-obtain.
Enter in your primary DNS as: 85.215.57.182 and click Confirm.
Click Back initiating a connection test when prompted. Hold B when you see the DNSpresso Splash screen.
Section III: Making a NAND Backup
Navigate to nanddumper using the GamePad and press A to launch it.
Use the Wii U GamePad's D-Pad to enter the following configuration:
Dump SLC: yes
Dump SLCCMPT: yes
Dump MLC: optional
Dump OTP: yes
Dump SEEPROM: yes
Press the A button to start the dumping process.
When the process completed, power off your Wii U, take your SD Card out of the Wii U and plug it into your PC.
The files will appear on the root of the SD card.
To make sure you don't lose the files, copy the slc.bin, slccmpt.bin, seeprom.bin, otp.bin (and if you chose to go with a full backup, every mlc.bin.part) file to your computer.
Delete the files from your SD Card to free up space.
Section IV: Installing PayloadLoader
Take the SD Card out of your PC and plug it into your Wii U.
Launch Settings > Internet > Connect to the Internet > Connections
Click on the network you previously selected and initiate a connection test.
This time, when you see the DNSpresso splash screen hold X.
Navigate the list using the D-Pad and navigate to the installer environment, press A to launch it.
Press the A button to check if you can install the PayloadLoader.
It should now tell you that the PayloadLoader can be installed onto the Health and Safety Information app.
Press the A button to select Install / Update.
You'll be asked if you are sure you want to install the PayloadLoader. Use the D-Pad to select Install and press A.
After installing finishes, press A to shut down the console.
The remainder of the guide is the same. Please continue to Autobooting Tiramisu on the Wii U Hacks Page linked below.