Hi Rasko,
first of all, you have to save your token from first API call into a variable.
Then, please try following code:
TestObjectProperty prop = new TestObjectProperty()
prop.setName("Authorization")
prop.setValue("Bearer " + yourToken)
List<TestObjectProperty> headers = new ArrayList<>()
headers.add(prop)
RequestObject reqObj = new RequestObject()
reqObj.setHttpHeaderProperties(headers)
reqObj.setRestRequestMethod('POST')
reqObj.setRestUrl('https://www.yourserver.com/api/endpoint')
def getResponse = WSBuildInKeywords.sendRequest(reqObj)