...React to the message in #giveaways to enter...
I don't see any #giveaways to enter.
All I can see is the VERIFICATION server, GiveawayBot, and AntiSpamBot. Where to apply?
Please be more specific use screens to show how to do it.

Even when I try to message the GiveawayBot using the command "!ghelp", I got a response with an error message.

After a while, I found that after registration to the Heat.GG server I have to go the server avatar, right-click on it, choose PRIVACY tab and click again, to be able to see this setting:

So now I can see and write messages to bots and other server members but still haven't found this giveaway

I think you should add such information in your first post for members who are not so familiar with Discord. It would save a lot of time an nerves.

I am waiting for your help OP because I did all I could and still haven't found this giveaway

.
Sorry for the confusion.
Please change your Discord privacy settings to allow messages from server members.
Then leave and rejoin our server.
You'll now get a DM from the Antispam bot, with a captcha to fill out.
Then you'll be auto approved and able to join the giveaway by reacting to the message in #Giveaways