How to install virtualenv:
Install pip first
sudo apt-get install python3-pip
Then install virtualenv using pip3
sudo pip3 install virtualenv
Now create a virtual environment
virtualenv venv
you can use any name insted of venv
You can also use a Python interpreter of your choice
virtualenv -p /usr/bin/python2.7 venv
Active your virtual environment:
source venv/bin/activate
Using fish shell:
source venv/bin/activate.fish
To deactivate:
deactivate
Create virtualenv using Python3
virtualenv -p python3 myenv
Instead of using virtualenv you can use this command in Python3
python3 -m venv myenv
could you please provide more details, like
what OS are you using
what command did you run and displayed an error
do you have any screenshots you can share