If you want to walk on river Nothern Dvina then you have to go to rever berth. Don't mix it up with sea-river port which you see on photo. If you stay near this port and look to river then turn to the right and go about 200 m, then you'll see rever berth. Happy river walk!
This River station looks rather impressive but inside there is a market and I saw a booth selling air tickets and another one railway tickets. I couldn't find a timetable for river or sea transport anywhere. My guess, they just handle transport vessels there.
Outside there is one of the big local bus stations. You could take a bus to Malye Korely there (see respective page).
There are no longer any trams running although you will see the tracks.
From Moscow Jaroslav station it takes about 22 hours to reach Archangelsk.
If you want to use the left luggage, make sure you check the times. For instance don't check out of the hotel at 12 am thinking that you can then bring the bag there as it has a lunch break from 12am till 2 pm. As you stand in front of the station it is in a building on the left of the station on platform 1.
At Retschnoy Voksal (river station) there is a timetable for boats running in summer. Don't confuse this station with the big Moskoe Retschnoi Voksal!