In general, cryptos like Bitcoins are purchased on a specialized platform; there are many of them.
Most of the time you must register in advance and then buy and pay (usually by credit card or bank transfer. By paying by credit card (or cash), you will get your cryptos immediately.
We strongly recommend that you learn about cryptos with Bitcoins; then, if you wish, you can easily discover and use others.
For your first payments, as part of the procedure described above (FAQ: How to start whether or not you already have crypto-currencies?), a summary email will contain both the crypto address and practical tips to easily obtain cryptos depending on your country of residence.