I'll save too many recommendations because I think you'll learn everything you need to know in Bogleheads Guide to Investing. I think it has all the answers you're looking for.
My "advice in a nutshell" is that since you say you want to be conservative, you can dedicate your age in % of your portfolio to bonds. The rest should be stocks. If this money is in a tax-sheltered account (401k/403b/TIRA/Roth IRA, etc etc), just find a cheap bond fund (like the Total Bond Market index at Vanguard or elsewhere), then split the stocks between Total US stock market index and an int'l index. Call it good.
You can get a little fancier based on how much space you have in tax-sheltered accounts. Taxable accounts aren't good for bonds, but stock indexes are pretty tax efficient.
I'd recommend an IRA at Vanguard, but that's up to you. Do you have a 401k?
(FYI, Vanguard has great Target Retirement funds, which is pretty much set it and forget, with bonds and domestic and int'l stocks. You may get a little more sophiticated later, but it's a great place to park retirement savings.)
Best of luck to you.