| Well, I don't work with Audacity, but most of the times, those kind of problems happen because you haven't selected the proper recording source in your sound card. Double click on the little speaker you have in the tray (your screen's lower right corner). A mixer should appear, but this is the "playing" mixer. You need the "recording" mixer to fix this. In that window, go to Options > Properties. A "Properties" window appears with the name of your sound device. Select the second radio button "Recording". When you click on OK, the recording mixer will appear, and, most of the times, this only allows you to select one recording source at a time. Options vary according to the sound card, but try with "Line in" first. Anyway, try with each one until you get it to receive your bass' signal for recording.
Just in case you don't have a speaker icon in your tray: Go to Start > Control Panel. Double click on "Sound And Audio Devices" (I suppose it appears like that in English. Mine is in Spanish). In the window that appears ("Properties of sound and audio devices" or something like that) you'll find several tabs. The first one is named "Volume" and there you'll see a tickable box named "Put a volume icon in system tray" (Or task bar... again, something similar). After OK, you should see the speaker icon.
Hope this helps. Let me know if it worked or not. | 
