First stuff first you will want to understand a bit how does it work what is private key, what is public key and other stuff. There are some free courses on Udemy which will teach you the basics of bitcoin. Later on to buy bitcoin or ethereum or any other you will have to go through exchanges. Some popular exchanges are gemini, coinbase, bitstamp and many many more. Simply tell us what you are interested in and I could guide you more.

Don't invest more than you can afford to lose and don't simply rush in to buy without understanding a thing, I will highly advise you to look at Udemy (even youtube search should bring some educational videos) because you want some basic understanding about how this work. It will take me to much time to write every single thing here. So go there check it out and come here if you have any more questions.

And simply try to post in Beginners and Help section as you will there find more people who are willing to help https://bitcointalk.org/index.php?board=39.0