1. Follow Amazon's official setup guide from here for the installation procedure.
2. After the completion of the Alexa installation, install the requisites for Picovoice porcupine using:

sudo apt-get update     
sudo apt-get install python3-pip wmctrl xdotool   
pip3 install pvporcupine    
pip3 install pvrecorder    

3. Download the alexa_picovoice_trigger.py file from this git.
4. Create the Access Key in Picovoice console and download the keyword from Picovoice Porcupine git.
5. For voice activation, open a terminal and enter the following:

wmctrl -l    

Note the id value of the terminal in the extreme left.
6. Start the Alexa's Startsample.sh script from the same terminal.
7. Open the alexa_picovoice_trigger.py script and change the id value given here with the id value noted.
7. Start the Picovoice porcupine trigger using the following syntax:

python3 /home/pi/alexa_picovoice_trigger.py --access_key ${ACCESS_KEY} --keyword_paths ${KEYWORD_PATH_ONE}       

8. Now, Alexa can be triggered with Picovoice Porcupine wakeword engine.