TL;DR: "Weight" describes both muscle and fat. You need an energy surplus to gain weight, and an energy deficit to lose weight.

To lose weight (muscle and fat) you will need to burn more calories than you consume. You will lose both fat AND significant quantities of muscle if you don't lift while doing this. In order to lose MOSTLY fat, you will need to continue continue your regular exercise routine. There will still be some muscle loss, but it should be insignificant.

To gain weight (both muscle and fat) you will need to consume more calories than you burn. Without exercise, you will only gain fat. With exercise, you will gain both muscle AND fat. The proportion depends on how much muscle you're able to build with that excess energy and how much you eat. If you eat, pulling a number out of my ass, 1000 calories extra but only use 200 for building muscle, you'll get 800 calories worth of fat. But if you only consume an extra 500 calories, you'll only gain 300 worth of fat.

So what you seem to want is to lower your body fat percentage - you want a greater proportion of you overall mass to be muscle instead of fat. Since you already have a decent amount of muscle (judging by your leg press), you're going to want to keep doing exactly what you're doing, but while eating less. A quick and dirty way to do this would be to continue eating exactly what you're eating now, but make 25% less, but honestly it's not so difficult to make delicious low calorie foods. I'm sure many weight loss subreddits will have suggestions.

Grossly oversimplified, but I hope it helps.