First, create the Form with your print button:
-Create a form in Design View
-Make sure the Control Wizards button is turned on (the "Magic Wand" button in the toolbar icon is depressed)
-Click on the Command Button icon (rectangle) and place it on your form
-The wizard should now be activated, and will ask you what you want to do
-Under "Categories", select "Report Operations"
-Under "Action", select "Print Report", then click Next
-Select the report you wish to print, then select the rest of the options you want
-Save form
Now, tell access to open this form automatically upon opening the database:
-From the Tools drop down menu, select "Startup"
-Under the "Display Form/Page" option, select the form you create in the steps above
-Click "OK"
Now, when you open the database the next time, it will take you directly to this form!