Once we have added variables at project ,test suite or test step level we can use it in any of our test steps in a Soap project

Like in this example if we want to use the variables in our login test step we right cilick the area where we want to add the variable.Then choose get data and then choose relevant data from project ,suite or test case relevant to that Soap request

So after adding user name and password to our login request will end up something like this. I.e we don't have to hard code user name and password in this test step. We can get them from project level custom variables.

<username xsi:type="xsd:string">${#Project#username}</username> 

Where username is the name we gave to our user name property