You can always put them on the official invites/RSVPs and if you have a password, it would be best to put the password on there OR you can either take off the password or have them contact you directly after receiving their invite.
We included ours on the save the dates. This gave guests enough time to look over hotel options, day of timeline etc. far enough in advance for people who are traveling. We just included the website directly on the save the dates, no detail card.
We put them on the save the dates and on the information card that arrived with the invitation "for more information about accommodations, travel, directions and all things wedding....".
Adding this the STD helped out of town guests plan their trip [travel, accommodations airports, directions]. They can start looking into whether the travel is feasible in advance, so they are prepared to RSVP [this also helps them meet your RSVP deadline]. Having it with the invitation on the information card reminds them of the website, and a provides quick reference for making plans closer to the wedding