Delta airlines booking mistake?

I just booked my flight to Jamaica with Delta, who I'm not used to. I'm used to flying with Southwest but couldn't this time. Well I purchased my ticket and didn't see the option to choose seats so I paid for my ticket and just expected to get my assignment during check in. But my friend who I'm going with was able to choose hers.
So now I'm screwed because we're more than likely not going to sit together. Also I may be stuck with really bad seats since I couldn't choose. Is there a way for me to fix this? Any Delta flyers out there that can help me?

I fly Delta a lot and I'm always able to pick my seats. Go back to Delta.com, sign in and look for My Flights. Click on the flight, and you'l be given a chance to choose your seat. I never quite understand people who insist on sitting together- what difference does it make? But when a friend and I are planning a trip, we often get on our laptops at the same time, look at the seats available and click on adjoining seats.

If you purchased a "basic economy" fare then you are not eligible for seat selection; a seat will be assigned at check in. In that case, you likely won't be seated with your friend. If you purchased a "main cabin" ticket, then you should be able to log into your reservation (use your confirmation number) and choose a seat. If there are none available near your friend, she should also be able to change her seat if you can find 2 together. You should be able to look at your confirmation to see what type of ticket you purchased.

So I just created a dummy reservation. You should have been able to pick your seats towards the end just before you hit the checkout button. See if you can go back in to pick your seats. If not, call Delta to see if they can help assign your seats.

Speak to the airline - you may be able to pay to choose your seat

OR - you can just sit wherever you're allocated, and see your friend at the other end. It's not the end of the world.

If you do not want to change this in the computer, then download the app. See where your friend is (have to ask them first). See if there's a seat empty near by. CHOOSE IT! We often juggle our seats a few times until we get what we want. If you do it early enough, before everybody else beat you to it, it is easy. So either YOU have to choose near your friend, or you pick a seat with empties next to it, and THEY course to move near you. You should be together when you do this - or at least on the phone. If you call the airline, they do not have BOTH of you in the other unless you are together - so using your apps might be easiest. You will learn how to do this for the future!

There are classes of tickets where you don't get to pick your seat. It will be assigned 24 hours prior at which point you can try to change it.

Your best next step is to log into the Delta site using the ticket/record locator number you got via the email confirmation. You should see an option to change seats. Click that and see if it lets you or gives you other information.

Worst case is that you do the same thing within 24 hours of the flight and change it. The assumption is that either you or your friend will be in the middle seat, since you want to sit next to each other, so it should make it a little easier to switch with someone even after getting on.

If you bought a basic economy fare, then you can't pick a seat at check-in.
If you bought a ticket that allows seat selection, then there's nothing stopping you from choosing a seat right now on their website. There's also nothing stopping your friend from changing her seat so that you can pick two that are near each other.

You can go to your online account and try to book the seat now.
It may / may not let you.

if it doesn't let you, when you arrive at the airport for the flight, ask the desk agent, If you can be seated together.
If they can't, when you are on the plane, ask the people around one of you, if they are willing to switch seats so you can sit together. You will likely find someone interested especially if they are going from a middle seat to a window/aisle.

If you don't already belong to Delta's frequent flier program then join.

Then call Delta and talk to a human. Add your Skymiles number to the trip and ask about seat selection.