It is just simply do analysis using riks subroutine after you finished set up some constants to determine when the load would be finished and aferward you may obtain LPF from the history output.
However, it is better to have a look the link what Mr. Sohrab provided.
this is a stupid question...if you read abaqus manual then you'd know that it's printed in sta file as well as stored by default in history output...better recommendation would be to read abaqus analysis manual rather than asking in a forum