Login to your windows server and start Computer Management
Right click on Uses under Local Users and Groups and click on New User...
Provide User name and password and name
This is going to be my kind of service account and I don't want to change password, that's why I have chosen Password never expires.
Click on Create.
Remember your user name and password, we are going to use it later.
Right click now on Group under Local Users and Groups
And Select New Group...
Provide Group name and click on Add...
Type User we just created and click on Check Names button
And then click on OK. And then Create button on New Group dialog.
In the real world you add Service account in your Active Directory or ask you IT Operations to create a service account for you. But the idea is more or less the same.