It's important to note that harmonicas are sold in a particular key (normally stamped on the side of the frame), and therefore harmonica players pack a complete set of harmonicas to each gig.
Look on the side of yours and see if there is a small capital letter there, such as A, B, C, D, E, F, or G.
If you have one that is in the key of C, then it won't do you much good on songs in the key of D.
I use a harmonica (from my zippered arsenal of them) in the key of A for whenever I play Neil Young's song Out On The Weekend. I use the harmonica set up for the key of C whenever I play Hank Williams' Jambalaya.
Check out the pricing on a complete package of harmonicas. They really aren't all that expensive.
To answer the last part of your question, I recommend that you spend some time exploring youTube instructional videos, featuring lessons on how to play individual songs. You can spend money for some really high-quality lessons online, but youTube is free.
If you are a guitar player, you definitely want to get yourself an 'around the neck' harmonica holder that allows you to play and sing at the same time.