A red padlock is made by creating an accountant export.
To remove one:

1. 1. Be in either Money In or Money Out.
2. 2. Go to [File] in the top left
3. 3. Select [Accountant Export] and [Unlock Months]
4. 4. Tick the months you want unlocked
5. 5. Then click [Unlock] in the bottom right.

A yellow padlock is made by reconciling your month.
To remove one:

1. 1. Go to the Bank Reconciliation for that month
2. 2. Click [Unlock] in the bottom right.