Rivnuts from Homestead, PA on 6/6/2019 6:54:27 AM:
The actual "distance" is short, perhaps 1/2 mile. However, you must cross the river to get to Harpers Ferry from the C&O Towpath trail. To do so, you must travel across the pedestrian portion of the railroad bridge across the river. To access the bridge deck from the C&O, you must go up a steel, spiral stair. Its not all that high of a stair and its quite wide. Nonetheless, you will have to carry your bike and gear up those stairs. Once on the Harpers Ferry side of the bridge you can ride to the B&B albeit with a manageable uphill grade.
I can't comment on the bike parking situation directly. The only B&B I've stayed at in Harpers Ferry did not have a specific bike storage area but did enable bikes to be locked to an outdoor railing just outside the B&B. Just call your particular B&B to determine their bike parking situation.