This is a very simple process, though more paperwork requirements than a DBA
In basic terms all you have to do is (this is assuming your state is like Michigan)
Download the LLC application from the states website
http://www.dleg.state.mi.us/bcsc/forms/corp/llc/700.pdf
You will find out that it will cost more money. You just can't go to the county clerk and register a DBA for $10 and be done with it.
make sure certain paperwork is filed before, if needed, such as
LARA - Naming a Limited Liability Company
Don't go "bonkers' when you see all the forms which may not be necessary (this covers individuals and hundreds of people sized companies)
Document Management Results
there's alot of information with it that you should read, such as on Michigan's site - see Filing Rquirements on the bottom left
LARA - Limited Liability Companies
There are LLC filing requirements and fees associated with an LLC versus a DBA (Sole Proprietor) - at least in Michigan
http://www.michigan.gov/documents/dleg/BCS_CD_265_281962_7.pdf?20130823133901
Fill it out, submit it. For Michigan it's $50 registration
You just need to know your company category, and do a name check
and change business cards, et all as you have to have "LLC" on all forms of marketing.
but the process is simple as an individual
it also protects you better.
Each state varies so check your states website first
If it all seems too complex, talk to an accountant.
It's better to get it right, and quickly than to have to figure it out later and correct things (those fees can add up fast)
An Accountant should really be able to do all of this in an hour or two if you are completely prepared.