Read Pamphlet
The Pamphlet lays out how the next week or so of your life is supposed to go:
• You inform your Family of your invitation, and they inevitably throw you the grandest Celebration they can. (In reality you expect they will glare and purse their lips, wondering just how to kindly inform you that you mustn’t go.)
• You pack a modest amount of Belongings into a Case that you can comfortably carry yourself to Armigette City, however far away it is from your Home. (In reality you are not even sure whether there is such a Case in the House, let alone whether you would be allowed to take it. You are also surprised to find out that the City has a name.)
• On the day appropriate for your Departure, assuming that you will arrive at Armigette City on the Acceptation Day, your Family will see you off. Traditionally this includes a Gift of a work of your chosen Vocation; the last one you will accept from anyone else before spending the rest of your life creating them for yourself. (In your case, that means your Sisters would give you a Dress, and from then on you would wear only that Dress or a Dress you made yourself. In reality, of course, you are sure they would do nothing of the sort to thank you for abandoning them.)
• Upon arriving at Armigette City on the Acceptation Day, you will find your way to the assigned House and receive further Instruction.
There is a bit at the back that explains how you might think that your Family will resist your Opportunity to Vacate. That you might think that they think you are trying to abandon them. But that this is probably not the case, and that in fact they will surprise you and be quite supportive. You are pretty sure this bit does not apply to you, and the person who wrote it was probably thinking of other Families.