My father-in-law had undergone transurethral resection of the prostate (turp). What do we need to do for him at home?

Very little. Very little has to be done, if he goes home with a catheter, you have to empty the bag when it is filled, slight bloody urine normal if bleeds call his surgeon. If come home with out catheter watch for urinary retention, slight burning is normal make sure drinks plenty of fluids. And take him to follow up visit.