Upon plan creation your first installment is charged immediately. Future monthly installments are automatically charged each month on the anniversary of your first payment.
In addition to your monthly installment payments there is also an Authorization to guarantee your purchase. An authorization for up to the full purchase amount is put on hold on your card upon plan creation.
This is not a charge.
These authorizations temporarily reduce the amount of credit available to you, but again, are not a charge and are required to guarantee your full purchase amount.
For most plans the authorization will disappear within 30 days or less of your purchase. For some plans the authorization will be periodically re-authorized, at lower amounts as you make installment payments, until your plan is complete.
The length of hold on your funds is always determined by your bank or credit card provider, so contact your financial institution directly for questions.