To know how to work on other assertions, do check Assertions in SOAP UI link.
SLA Assertion is used to check whether the request executed in given time.
Let's create SLA Assertion,
Enter the maximum response time as 200 and click OK.
Now we see that the Response SLA assertion passed as the total response time it took to execute the request is 163ms.
Let's set the response time to 150ms to check the assertion.
Now the assertion failed, as the time taken is more than the maximum response time given in the assertion.
for SOAP Fault assertions, check the link.