gastric bypass

Talk to your doctor... but I do know when I had abdominal surgery (not gastric bypass) I was quite bloated & swollen in my belly for several weeks- it's possible you have the same which would make your weight higher.

Logging your food in MFP is quite easy, there's probably a tutorial on here how to set up an account & log food, but you probably want to base your calories & macros off your doctor's guidelines rather than whatever the app calculates for you. You can change your goal calories & macros in the "goals" menu.

I agree with speaking with your doctor and asking for a referral to a registered dietician (not a nutritionist because they are not licensed or registered) so you can figure this all out.

I had surgery on May 26. I spent a week in the hospital with complications. I didn't lose a single pound, AND I was on a clear liquid diet for a week. A week later, I started melting.
Then I hit a plateau where inches would melt off.
Then weight.
Then inches.

Take your measurements, weigh in weekly, and follow the diet to a T- which you should still be all liquid, MAYBE pureed. Don't rush the process!

I would recommend a dietician over a nutritionist. Anyone can call themselves a nutritionist, but dietitians have gone to college and are more knowledgeable with health and nutrition. I saw my doctors nutritionist and she told me now to eat less than 2k calories or I would go into starvation mode and gain weight. I would not recommend one.

I'm going to link you to the stickied helpful threads: http://community.myfitnesspal.com/en/discussion/10300319/most-helpful-posts-general-diet-and-weight-loss-help-must-reads#latest . Those are for later.

I had a sleeve in 2012. At this point, you are most likely still on liquids & you should have been given a pretty detailed eating plan from your surgeon with the number of calories to try to take in every day, the amount of protein you should be eating, & whether you should be on clear broth or purees. If you did not receive one, you should be blowing up the phone at the doctors office immediately. It's important that you don't begin solids too soon because you need to heal.

Once you can start eating solid foods, your doctor should be giving you guidance there as well. What your initial daily calorie goal should be, the amount of protein to get in, what foods to avoid. I know with gastric bypass, you will generally have to learn what will personally be acceptable for you & not trigger dumping--it's not the same for everyone.

You can use MFP to track all of your intake. You need to get a digital food scale & start weighing all your solid foods in grams & using measuring cups & spoons for the liquids. You should log everything. You start building up your list of favorites & frequently eaten foods so it gets faster & easier to use the longer you do it. You will get a warning that you aren't eating enough calories. You can ignore that. MFP will continue to track your totals & save your data.

Don't worry. If you follow your doctors advice, you will lose weight. This is the time to start building the habits that will sustain you once you reach maintenance. I honestly don't think I would be where I am now (at a normal BMI) without having used MFP to keep track of everything.