You can use DataSource to bind the ArrayList to your combobox:
yourComboBox.DataSource = yourArrayList;
Use DisplayMember and ValueMember to select what is displayed and what is evaluated as Value of the item:
yourComboBox.DisplayMember = "Displayed thing";
youtComboBox.ValueMember = "Evaluated thing";
If you don't specify the DisplayMember, the ToString() will be called on each item to get the displayed string instead. In your case, it looks like you have an ArrayList of string, so you don't need to specify any values for DisplayMember and ValueMember.
NOTE: You should use a List<T> instead, it would be better. ArrayList is just an old stuff.