Hi, newbie using Saxo for US Stocks. Can I sell a stock (e.g. few hours) after I buy it, or is there a settlement time needed? If yes, how can I know when i'm clear to sell it?

Yes. You can sell on the same day of purchase.

Settlement takes 2 to 3 days. But its the same for buy and sell.

So if you buy on Monday, the stocks will be in by Thursday. However, you can also sell on monday since the stock will only be deducted on Thursday.

But if you are new, I wont suggest you to do 'trading', which is buying and selling for profit on capital. If your aim is for investing, you should be looking to hold long term.