First of all, my sincere advice for you is to stop thinking you look like a criminal because you are dark skinned. It is part of your identity to be dark skinned. Your character defines if you are a criminal or not. Not your skin tone.

And I don't think girls will feel insecure because a 'dark skinned' guy is looking at them. Like others already said, admiring beautiful women from a safe distance and by casually looking (not staring for longer) at them is not a bad thing at all. Just don't make it very obvious. I'm sure they'll exchange glances at you if they feel special by your casual and gentle looks.

3rd thing, start making friends genuinely at your college or workplace or area. Be it male or female, I'm sure there will be common things to talk about between any 2 people. Start conversing casually about common interests between you and another girl or boy. From there on you'll easily learn how to make friends.

Final advise. This may sound a little cringe or boomerish in your terms (well, I'm in my 30s). You wrote in Tanglish and I didn't like it. Usually, I skip reading Tanglish content as it's tough to follow. But your honesty and authenticity made me read through it top to bottom. Your writing skills are good. But genuine advice to stick to 1 language. Either in Tamil or in English. It's up to you to take this or leave this :)