There are two issues. I am attaching files. Please guide, how to work with Jenkins, with no errors.

I am trying to explore Jenkins and use it, first time when I run Jenkins it opened up fine. Changed the Java_home variable from system variable to user variable. Couldn't open Jenkins in Localhost:8080. and it was not running in command prompt. getting error.

Deleted Jenkins, downloaded it again .  when I gave java -jar jenkins.war  command in command prompt, got one error in command prompt .Attaching the file. Could open Jenkins in local host, but got an error when click on Manage Jenkins >Manage Profiles. Not its fine but getting same error while clicking on Manage Jenkins > 

Global Tool Configuration, Configure global security ConfigureCredentials.

Attaching another file

https://www.screencast.com/t/muxVdffJ