The bag you have can be made to work well enough, but there are a bunch of variables. How large is your frame, or at least the distance from your bars to the top of your tire? The bag you linked to is the long top load zoom and is speced at 13 inches. Assuming that you are on a larger frame the next challenge would be your controls, brake and shift cables, have you test fit the bag to make sure that it does not interfere with you cables either straight or at full turn of the bars? If you have a green light on both counts the next stop is ensuring that you have sway under control. If you have a front rack of some kind, preferably with a platform and backstop above your tire I would connect the lower d-rings to that. IMO your best bet for a positive connection is heavy duty zip ties, but that kind of negates easily getting the bag on and off the bike. Next in order of preference would be leather buckle straps like the heavy duty ones sold by Acorn Bags (google it). While the velco straps my work for a bit, the on and off cycles combined with general wear and tear will result in less than perfect performance in the long run.
As long as you are ok with water resistant this should get you started. In the last 6 years I have seldom left the house by bike without a camera of sorts. My first set ups were exactly what you and I are talking about here. I like having the cameras suspended between the drop bars. IMO it is the area of least shock/shaking and the bars provide a roll cage of sorts if you were to dump the bike. I have had it happen at moments of inattention while stopped. Get started with what you have, the gear is meant to be used, you will break it eventually. Move on to better gear. This path is how I ended up with a company selling bikes designed around front loads and good handling. I now prefer Micro4/3 cameras for the versatility to weight ratio, but carried my Canon DSLR for a few years before switching all the way over. I like to have my nice camera with me, because it is what I like ot take nice pictures with while out on rides. I like it up front where I can get to it and feel it is protected. I like to keep my cameras in top load zoom bags so that I can easily take them with me and leave the bar bag on the bike.
Most importantly have fun on the journey, take lots of pictures and learn as you go.