I am in Connecticut/ north east. Have been about 40-50 degrees on average lately

How much of your total lawn are we looking at? If you don't have an enormous lawn I would start over. Just do your best with the lawn for now and spend between now and August learning about lawn care. It won't take long if you search this forum. I think you will get a much better result, particularly on such a small plot of lawn, if you start over. The objective is to reseed in late August or into September. You have to kill off the lawn first with round up and that needs to begin about 3 weeks before seeding. You do not have to mess with the ground itself, like aerating or tilling it up, so the "starting over" process really isn't that hard and you will have a fantastic lawn come the following spring, given the right care.

Other than that, I'd suggest mowing low, maybe 2" to clean things up from the over winter and you'll get a better look at the bare spots and what you really have to deal with.

Your first lawn so I see you're not starting out well. Let's fix that. To start with, weed n feed is a beginner's mistake. Sure there are some people who make that stuff work, but you, as a beginner, will not be one of them. So as a beginner, there are some things you already need to unlearn. Here are the basics of lawn care.

Routine stuff: watering and mowing. These generally get done most frequently. Mowing is done weekly during the season, but watering may not get done every week. It depends on the temperature. Deep and infrequent is the mantra for watering. Deep means 1 inch all at one time and not spread out over a week. Put some cat food or tuna cans in the yard and turn on your sprinkler(s). Time how long it takes to fill all the cans. That is your watering time from now on. As for frequency of watering, that depends on the air temperature. For temps below 70, deep water once a month. Mother Nature almost always takes care of this. For temps between 70 and 80, water once every 3 weeks. For temps between 80 and 90, water every 2 weeks. For temps between 90 and 100, water once a week. Remember, deep water every time.

Mowing: mulch mow at your mower's highest setting.

Less than routine: fertilizer and herbicide. Fertilize for the first time in late May (Memorial Day is easy to remember). Fertilize again in early September (Labor Day). Fertilize again in late November (T-Day).

Herbicide: NOW is the time to spot spray weeds. I don't see any weeds, so don't spray unless you have weeds. Generally Weed-b-Gon is sufficient for spot spraying.

That should get you started in the right direction.

@dchall: I think your watering recommendations are more realistic for warm season, deep rooted grasses. I tried those recommendations on my KBG here in NJ and you simply cannot go 1 week at 90 degrees without watering even when you mow at 4 inches. It's something I've been keeping close watch on over the years and I think Joe had the same experiences that I have. For me, I wait until I see the first signs of stress, which might be only a day or two in real heat. Many of my neighbors water every morning or maybe every other morning in the summer. I know that is not recommended but I have to say their lawns look fresher than mine in the summer heat. Oh, and I've been getting hammered by fungus every year while most of their lawns are just fine. Go figure!

I would probably not get crazy until fall. For now, put down fertilizer with crabgrass preventer. Then just the usual lawn maintenance stuff (as described previously). A little TLC goes a long way, especially if you are just taking over this lawn and it has been neglected.

What should I use for all that then? @mishmosh

Something like Scotts Turfbuilder with Halt's Crabgrass Preventer