Question about healthy weight gain

I've a strange request.

I am almost 6 ft. tall and weigh about 75 kilos. I'm more concerned about my health than my weight, however, over the last month (during which time I've done a few flushes and recently started on Colosan) lots of people have started telling me I look really thin, if not sick. My face is elongated and is particularly thin.

I am a 33 year old male and would like to put on weight safely. But I guess that means eating fast food and bad food. Is there a healthy alternative to put on weight? I'd like something that's relatively easy to obtain. I live in an area where there are not a lot of health-food stores or health-conscious people for that matter.

I'd like to gain 5 or so kilos. I'm tired of hearing that I am so thin.

Thanks for your suggestions in advance,

Best wishes,

Brett.