i use a financial advisor now, but when i first was starting i did it all myself. if you are going to be hands off and let it grow with like index funds, run it yourself, if you want to get aggressive with frequent trades and actively manage it (tax loss harvesting and other aspects) you might have a financial advisor do it.
As for how to run it, i say it's dependent upon your options. when i started mine, my employer had a deal with fidelity that made all account types free on that site (this was at a time where that was not the case, there were account maintenance fees everywhere) now i think most of those fees are not around so go look at a few and see which interface you like best (because there are some bad ones - Merril Lynch) and pick one.