It is that time of year as the new board came into leadership beginning on July 1st.  So what happens next.
First, we want to make sure that we have closed out the previous year books by having a reconciliation done.  The reconciliation will be done by 3 people.  The forms can be found on the Texas PTA website.  
Second, now that you have had the reconciliation completed you can now move forward with changing your signers on the bank account.  Depending on the bank.  Some banks will require that all 4 of you go at the same exact time to sign the new paperwork.  Other banks will allow each member to come in separately.  You are going to have to check with your bank on their procedure.  The Secretary should actually start the process at the bank.  She should take the minutes showing who was elected into the positions.  She will have to also sign the proclamation to verify that the three people coming into the bank are indeed those from your organization allowed to be signers on the account.  The Secretary cannot be one of the signers.  The President and Treasurer are automatically signers on the account and then the President will appoint a 3rd signer.  There must be three signers on the account and none can be related by blood or marriage.  I would also highly recommend that you do not choose your best friend serving on the board as this can cause issues with how it looks to others. Note:  some banks require you to name in your minutes who the signers will be and they also want your minutes to include the name and location of your bank in the minutes before they will proceed.  Better prepared with too much in your minutes on this than to have to make multiple trips.  
I do also want to make an addendum to the information above.  If the President is employed by NISD then they may not be signers on the bank account and they must appoint someone to be a signer in their place.  An employee of the district may not hold the position of Treasurer.  Remember that no signers can be related by blood or marriage and/or reside in the same household.  This is not true of Guest educators, just full-time NISD employees.
As I said it is best practice to check with you bank about what they require.  Each financial institution is different in their rules and procedures.