Unable to access jar jenkins war file

Question

Hello Edureka team, I am facing with one problem and it is to install Jenkins, I tried a lot of methods to install and configure it , but is not working:

1. when I download jenkins.war , I go to cmd and type "java -jar jenkins.war" and it says "error: unable to access jar file jenkins.war"

2. I set environment variables for Java and Jenkins, but this one also did not work

Can you help me to find solution? And what I am doing wrong?

Looking forward for your advices. Thank you