Just to add to what schwifty said, you can bid on another domicile on day 1 of indoc (should you be so lucky with timing), but only on the same equipment. These usually convert fairly quickly because there is no training involved. However, you cannot bid on a new fleet (equipment) because there is a 2 year "Category freeze" (aka seat lock - or more accurately, a bid lock), that can only be broken in a couple of specific circumstances.
1. As a NH, if you want to bid a domicile that does not have your original equipment, you can bid for that starting at 1 year, but any remaining NH seat lock is added to your new 2-year seat lock. IOW, you will be seat locked in that new equipment until 4 years on property.
2. Your very first Captain bid will break any seat lock. But again, any remaining seat lock is added to your new 2-year seat lock as a captain.
3. If a new equipment/domicile combination is opened, anyone can bid on it regardless of seat lock.

Keep in mind, per the PWA, if you still have a category freeze/seat lock on day 1 of the conversion window (usually the 1st of the month following bid closing), you cannot bid (other than to change domicile on the same equipment). The company can waive that at is sole discretion - it can happen, but not that common. Because we have infrequent and irregular bid cycles (4-5 per year on average), and the conversion windows are either 210 days or 365 days, it is possible to be awarded a bid to a new aircraft and/or domicile, but not actually convert until nearly 2 years on property anyway. Bid accordingly.