Olaus Ogland/Tagland from Stavanger

Hi! My GGrandfather, Olaus Ogland (changed to Tagland in the U.S.) was born in Stavanger Jan. 3, 1850 and came to the U. S. with his brother, Ludvig Ogland, who was born in Stavanger Jan 9, 1953, sometime in 1871. I don't know where they left from or what port they entered the U. S. Olaus returned to Stavanger sometime around 1874, married and had 4 children and they came to the U. S. again in either late 1883 or early 1884. Once again, I do not know where they left from or what port they entered the U. S. Ludvig Ogland born Jan 9, 1853 Olaus' family: Olaus - born Jan. 3, 1850 Wife - Bertina Kvaleberg - born Mar 26, 1851 Daughter - Talette - born May 3, 1877 Son - Orly - born Mar 15, 1879 Son - Andrew - born July 6, 1881 Daughter - Birdie - born Dec 12, 1883 I would like to try to locate the ports they left from and where they arrived in the U. S., dates of departure and arrival and what ships they traveled on. I would greatly appreciate any advice/information on how I could find this out. Thanks! Mary