Start with the 2012 series
Arrow has its own show entry. Search Arrow, open the series and choose the episode guide. A query such as Arrow S2E3 can take you directly to a recorded chapter. If you are new to the show, begin with the first season instead of the newest dated result.
Keep your place
On the series page, select the last season and episode you finished and save the checkpoint. Your note stays in this browser. It does not mark every earlier chapter as watched or recover a timestamp from another service.
What about DC crossovers?
A season list for Arrow is not a complete crossover order for every connected series. The Flash, Supergirl and Legends of Tomorrow have their own episode guides. Use the exact show name when moving between them, and avoid assuming an episode in a different show has the same number.
Explore the Arrow and DC collection or find Arrow. Viewing options should be checked for the season you actually want.