I use nutracheck as a calorie counting app. It's not free, but think I paid about £30 for a year so it wasn't extortionate. The key draw for me is I can batch cook, create the recipe on the app, let the food cool and then weigh it. Then each time I have some I can weigh out the portion and add it from the app. I haven't found anything similar that does it, and I have similar meals a lot (Dal, chilli etc).
To weigh food you only need basic digital kitchen scales and the easiest thing is to put your plate on the scales empty, set it to zero, and add each item. So you can record say, 200g salmon, 20g butter, 100g green beans etc.
It sounds a bit of a faff but it soon becomes habit, and the really key thing is you get an idea of what to look for. Eg these days I don't weigh out my breakfast because I know that an extra spoon of bran flakes won't make a difference - but how much butter or mayonnaise I use on my lunch definitely will!
Lots of people will tell you to use an online calculator to tell you how many calories you can/should be eating, though I find it varies so much I've never found it particularly useful. I think the easiest way is to track your calories for two weeks without trying to change anything. That will tell you how much you're typically eating (the app can give you an average person day). Then aim to go lower, 500 a day if you can, or 300 a day if you want something a bit more manageable. Doing it that way will also help you to see where is easiest to make changes. For example, I was very aware that my stress snacking on chocolate wasn't great but was really hard to stop. I didn't realise how many calories were in some of the crap supermarket sandwiches I grabbed on the run at work, and giving those up was much easier!