This can be translated as "Enoch had a son and named him Irad" or "Enoch became the father of Irad." Verse 17 told about Enoch being born. Verse 18 tells about Enoch having a son. The implied information is that Enoch grew up and married a woman. This can be made explicit as it is in the UDB. (See: [[rc://en/ta/man/translate/figs-explicit]])