First, getting a letter during sophomore year (especially since it is September, you just started) is pretty early. Many schools allow the letter to be 2 years old but....why are you getting them now? Also, why are you asking "what do I do with them"??? It's best you shoudlnt even TOUCH them!!!
Dude, not trying to be harsh, but it sounds like you have done ZERO research on the application process, plus, you are only a sopomore. You have other worries right now.
When the time comes, you have to check with each school you apply to as what they require for letters, and who they have to be from. Also, many schools, if you search their admissions site, will have guidelines about what letter writers should address in their letters or even have evaluation forms for them to fill out instead of writing a letter.
Bascially, dont worry about this stuff at this stage in the game. Plus, most of your info will be found by actually taking the time to research each individual school as well as the AACOMAS process, which your pre-med advisor SHOULD help you with. SDN is great, but if you decide to just throw up questions on it all the time instead of researching, you will become very frustrated in the process.
Not saying you are/will do this, but just telling you ahead of time, because some do.
PS--Study hard for the MCAT next year.