Field A1 on the Baltic map has one shore battery. When you start up AH you get the AH splash screen and a clipboard with some options. Click Choose Terrain, select Baltic then click OK. Now click Offline Practice and you should be at A1 on the Baltic map. And as you guessed, the hanger is the right place to go. From the hanger, right click in the middle of the plane selection and click ALL. The clipboard will refresh to show you all equipment available. Click Gun Ship or Field and a field layout will open where all the gun positions are shown with yellow dots. Move your mouse until you see 8” Single and then click the yellow dot which will then turn green to indicate that it is selected. (Hint: the SB is below and to the right of the field. Some filed have their SBs intermixed with the soft guns and you have to use your mouse to find the 8” Singles.) Now hit the H button on the clipboard as you would with anything else and you will be in the shore battery. Of course there won’t be anything out there to shoot at. End your flight and move to a port where you can practice shooting at your own task group.
Have fun.