Things you need:

• Picasso96 driver from Aminet or P96 driver from iComp.de
• Updated PiStorm install with the PiStorm utility HDF

For the Aminet shareware driver go to here to get Picasso96.lha
For the iComp.de driver go to here (you must be registered and logged in) and pay what you want (€8.96 minimum)

Make sure you have a recent build installed from the main branch. make sure the emulator isn't running. If you set it up as a service as per boot-scripts then you need to stop the service:
sudo systemctl stop pistorm

Then make sure you have the latest stable version

cd ~/pistorm
git pull --ff-only 

NOTE: if you have made any changes to any original files (default.cfg, A314 config or saved any changes to the pistorm drive) then the pull will not work. you must backup your configs then force a pull:

git reset --hard

Then restore your changes, preferably into a copy of the new default.cfg and with a different filename.

Build the new version (if there were changes)

make clean
make

And update the bitstream if necessary:

./flash.sh

Use your preferred method for copying the picasso96.lha (or installation files from iComp.de) to your disk image. One way is to mount your disk image in UAE and use a shared folder to copy the file across.
The archive needs extracting.
Dopus is one way - using lha x (if setup)

or in a cli window with lha setup in the path, navigate to wherever the .lha file is placed and type:

lha x picasso96.lha

To extract it into the current folder.

The ouput should look something like this:

Jens from iComp recommends not installing under emulation so if you are using WinUAE to transfer files, now would be a good time to switch over the real Amiga.

Before running the PiStorm emulator, check your config has the following settings uncommented with nano <name_of_your_config_file>.cfg

setvar rtg

and

setvar piscsi6 platforms/amiga/pistorm.hdf

Now let the emulator run either by restarting the service sudo systemctl start pistorm
or by launching the emulator directly sudo ./emulator --config your_config_file.cfg

Once workbench is booted, find the place where you copied the extracted files to and go into the Picasso96Install folder and launch the Setup application.

For all prompts Click Proceed or Proceed with Install except for the prompt for selecting a Graphics card.

You should be able to select no cards and still proceed with the install.
However if after this prompt:

the installer aborts, then select a card such as Picasso IV

Continue with the install by selecting the default locations (e.g. SYS:Libs etc) until you are prompted for the P96_PrinterPatch:

Select No

Continue to select Yes or Proceed, or Proceed with copy until the installation is complete.

Now go to the Pistorm utility drive and Launch rtg -> PiGFX Install -> PiGFX Installer

Again select all the defaults and when prompted find the location of the extracted Picasso96Install folder from previously.

Click Proceed through to the end of the installer.

Go to Workbench -> Prefs and open Picasso96Mode

Then Select Pistorm RTG (1) PiGFX and scroll down and click Save (it may be off the bottom of the screen but it will scroll)
You will be prompted to reboot, so let it.

Once you have rebooted, go back into Workbench -> Prefs and open Screenmode
Select the mode you want (try 1280x720 and HiColor first) and click Save.
The Pi will now switch it's HDMI output to display workbench so make sure you have a monitor attached and switch to it (If the Pi was booted without a monitor attached it may default to the composite out. You'll need to change some HDMI settings in config.txt to prevent that)

Sit back and enjoy a cold drink with your new RTG enabled workbench!