Those exchanges allow the purchase of cryptocurrency either via a card payment, or via a wire transfer / SEPA deposit from your bank account. They will also require some sort of identification because they are bound by financial laws related to customer due diligence and AML (anti money laundering) legislation. You may be asked to provide identification information such as an ID card, a passport or a proof of address. Note that some sites have different thresholds to buy cryptocurrency or withdraw fiat currency to your bank account based on the level of identification info you have provided. If you are into this seriously, make sure to provide the info necessary to the level you want to reach in time, not at the last minute when you want to liquidate your positions (or said differently, when you want to cash out).
What would make me sell: Sometimes there are good reasons to split up. For this part of your journal, compose an investing prenup that spells out what would drive you to sell the stock. We’re not talking about stock price movement, especially not short term, but fundamental changes to the business that affect its ability to grow over the long term. Some examples: The company loses a major customer, the CEO’s successor starts taking the business in a different direction, a major viable competitor emerges, or your investing thesis doesn’t pan out after a reasonable period of time.