Hello there!
You may not have had the opportunities to create and maintain many friendships as a child, but this does not in any way mean that you're incapable of making and maintaining friendships now! - Always remind yourself of this fact!
In my opinion, the ability to make friends and socialize is just like any other skill that some of us are great at and some of us aren't. In the end, this skill is still a skill - something that can be learned, trained and mastered!
From all the guides I've read regarding socialization and friendships, the foundation relies on striking up a conversation with somebody - This is the very start to making friends! Try going to a place where there are people who have similar interests as you... A specialty shop, tourist location, museum, anywhere that you may find interesting. Try to strike up a conversation with anybody about nearly anything! "Nice weather we've been having, huh?" "Oh, that movie is great!" "I was thinking of trying that, do you have any suggestions?" and so on. Smile, be friendly and seem interested in what they're saying, giving an appropriate and conversation-provoking reply.
Don't expect to make a dozen friends each time you go out. Don't even expect to make one each time you go out. Go out with the goal of just talking to some new people. If they are interested in what you have to say, they will ask you some questions and you might just get caught up in the conversation.
Don't get discouraged if they don't seem interested in talking to you either. Don't even take it personally! For all you know, they could be very busy or preoccupied. Just always be friendly and just try to have a fun conversation. If you end up having a very interesting conversation with someone about a certain hobby or interest, try asking them if they'd like to get together sometime! If you and the person you're talking with like fishing, why not ask them to go on a short fishing trip with you sometime?
If you feel that you just don't know what to say to people in order to hold up a conversation, try chatting with some people online. The best thing you can do is ask about a subject that they may have mentioned, showing that you have interest in their life. As you start socializing with people and gaining friends, just try to be the best darn friend you can be! Be loyal and helpful to your friends and they should do the same for you.
Those are just a few suggestions I have for making friends and being social. If I think of any others, I'll surely post them!
Just try to remember that all friendships start with conversations and similar interests. By using conversation to find out if somebody else has similar interests as you, you'll soon be finding those people who you get along with, have similar interests with and have good times with...AKA friends :)
Remember that once you start making a few friends, they may introduce you to others who are similar to them, giving you access to a larger social circle.
I hope your search for friends and socialization goes well!
Moose
PS: If the people at work are friendly, why don't you try getting a few of them together for a casual relaxing dinner or something? Take a break from the work environment and just relax with each other over a nice meal!