Just echoing what another comment said: it’s rarely a good idea in the long run to buy an IPO. Not financial advice. It’s one of those things where if you have to ask how to do it, you probably aren’t wealthy enough to be speculating at this level.

Would you buy a gaming console for a high price from a company that’s never shipped a gaming console? Maybe, but you’d wait til it’s been reviewed by someone else on YouTube or something.

I have tried a couple of IPOs

You indicate your interest. Also start funding the account. So you fund 7000 for 100 shares at 70. Then they announce the price is 75. You must change the order to fit the funds or have extra money. Of course you can opt out or change the quantity anyways. But I think in both the cases I actually went ahead (Reddit and figma), I had to reconfirm the quantity. You can't be away from the network.

You commit to your broker before, if you're big enough of a player. They'll mostly have allocated to their biggest clients and such.

Pretty hard to get in on a hot IPO, though, as the shares will go to their favorite clients (those with the most money).

I just 'bought' some through ing-diba, you can set a limit.

You don't need a broker. Use Saxobank or similar.