Make sure your liquid node is running on liquidtestnet with rpc server enabled (elementsd, or elements-qt with server=1 in elements.conf).
Also , you'll need an existing default wallet on that elements node, something like this:
elements-cli -rpcport=18891 -rpcuser=liquid -rpcpassword=liquid createwallet ""
cd src # or wherever all your projects are
git clone git@github.com:cryptoadvance/liquidissuer.git
# we assume that you have cloned specter-desktop in parallel with amp-issuer
cd ../specter-desktop # your specter-desktop is here
git checkout master # you need at least the master-branch
cd ../liquidissuer # jump back to liquidissuer
# Use the environment from specter-desktop
. ../specter-desktop/.env/bin/activate
# Install additional requirements
pip3 install -r requirements.txt
# Start specter
python3 -m cryptoadvance.specter server --config DevelopmentConfig --debug
Configure your specter to have the liquid node ready.
# Build
python3 -m pip install --upgrade build
python3 -m build
# ... and upload
python3 -m pip install --upgrade twine
python3 -m twine upload --repository testpypi dist/*