It's preferable to post as you go (better to gain an audience that way). When I started I posted three days a week, which might have gotten me more views, now I post twice a week due to my own time constraints though. But, no matter what happens, gaining an audience for a novel will be slow and it's up to you on how you want to go about it.
In regards to posting itself. I type it on software made for writing and copy it over, but you can also type it on tapas. No text files are required.