I'm a bit confused as to what you're asking for. The title says "1st & 3rd or 2nd & 4th Wednesday" which seems to imply that you want one reservation on the 1st & 3rd Wednesday, and another one for the 2nd & 4th Wednesday. That's easily accomplished by using the repeating option "Monthly by day of week", choosing Wednesday, and checking the boxes by "1st" and "3rd" (and similarly for the other reservation on the 2nd & 4th Wednesdays).
But your description seems to be saying something different. But that sounds to me like 4 distinct reservations, so I don't see how you could be more efficient than creating 4 separate reservations.
Or is it just one reservation which occurs on every Wednesday? If so, you would use the repeating option "Weekly" and have it repeat every 1 week(s) on Wednesday.
If it's something different from all of the above, please help us understand what you're asking for, perhaps with a specific example.
Questions that can benefit the larger community should be asked in a public forum, not a private message.