Holiday / Annual Leave is added to the account by default when your account is created:
These three leave types apply to salaried, hourly and zero hour staff, but these can be customised to your setup.
For annual leave, it is best to have it apply to bank holidays, and normal days. (which can be done in two separate leave types, or in the same)
If your holiday/annual leave type applies to all days, you will need to add the starting balance as the combined amount of holiday leave and bank holiday balance.
As for other leave types, holiday/annual leave can be set to accrue or deduct from a balance, depending on if it applies to salaried or hourly employees.