Creating an LLC actually has nothing to do with real estate. You could create an LLC to operate a food truck, sell shoes, or build websites.
The LLC becomes a separate legal entity, which can generate income and expenses, pay taxes, and own assets such as vehicles, furniture, fixtures, and equipment, or real estate.
Whether to hold real estate in your personal name versus holding it within an LLC depends on a lot of factors, such as the type of property, the type of financing used to acquire it, and your tax and liability protection strategies.
If you are planning to acquire commercial property, it often is a good idea to go ahead and get your LLC set up (because you might not have time to create a new one during due diligence on a real estate transaction).
If you are going to acquire residential properties using conventional residential financing, you may need to acquire them in your personal name (because conventional Fannie/Freddie financing is for individuals, not for companies) and employ other liability protection strategies (such as insurance).
These are all strategies to discuss with your CPA, attorney, and lender.
But note they will often give you conflicting advice! For example, an attorney will often tell you to create an LLC for liability protection, but your mortgage broker will tell you that you can't buy properties in the name of your LLC if you want to lock in a 30 year fixed rate with conventional financing.
So you have to take all of their advice under consideration and figure out what works best for you.
They advise, you decide.
To answer your original question: Yes, you can generally transfer assets into or out of your LLC at any time. Joe Smith the person would simply transfer ownership of the asset to Joe Smith Enterprises LLC. You would do this with a deed for real estate, or with the title for a vehicle, for example.