Running Appium Automation scripts with Android Emulator and IOS simulators

I am trying to run the Appium tests against Emulators and Simulators
Currently I have performed below steps

  1. Git Clone Repository - To clone the repo from the bitbucket
  2. Added below scripts in Script step.
    npm install selenium-webdriver -----> to Install the selenium webdriver
    npm install -g appium ------> to install the appium
    appium &>/dev/null &
    adb devices -----------> to check the servers are up and running.
    gradle test ------------> task to run the scripts.

I am getting the below error

org.openqa.selenium.SessionNotCreatedException at
Caused by: java.lang.reflect.InvocationTargetException at
Caused by: org.openqa.selenium.WebDriverException at

Please help in resolving this issue