I have flung a few arrows down range at different events, with very limited success, My 12 year old son has relay gotten into shooting and hunting and has asked for a crossbow for several years. I told him no that when I could afford it I would get him a compound bow. Bob has Developmental Coordination Disorder, compounded by ADD. I have watched him struggling with compound bows at scouting and 4H events.

I reconsidered and ordered him a cheap 150 LB crossbow, which I have not even revived yet. The reviews stated that the bolts that come with the bow are worse than worthless, and some reviews mention some sort of lubrication for the string. I have no idea what kind or size bolts to get or, string protection.

Could some one please guide me to some beginners information.

Look up the brand of crossbow and it should tell you bolt size and recommended weight. If it comes with bolts let him practice with those and all so if they break or get lost it isn't the end of the world.
As for waxing the strings, you can get it at Academy or any outdoor store you have around, it comes in little tubes like chap stick. Wax strings every 3-5 shots.
I'm sure by now you have got it and have it all figured out. Have fun with it and remember to watch your fingers cause it will get ya!

On crosbows, depending on brand, you will probably need lubricant on the rail as well as the string. IMO, waxing string every 3-5 shots is not needed, butfor the first couple of practive sessions, I would wax string after session. Look up this on YouTube and you should find lotsof info.