First you have to put your address in tec profile account and then they will send you. Thats what I did and I can see my blp"s in the explorer but it seems that I have to configure my desktop client now to point to mainnet. Can anyone help me please with that, how do I do that?

Look back a few posts to see the nethash and seed server I posted a few days ago. This data will get your desktop client on to the mainnet. If you haven't set the desktop client to mainnet, I'm left wondering what network the wallet you entered on the ico site is on... I hope that you didn't have your tokens sent to a wallet on testnet.

question:

All i have to do is to give my bpl token adress ( = wallet adress!?) on the ico site to claim my coins?

Yep-- create an address on mainnet and enter the address into your profile on the ico site.

Where do I find proper instructions to install a node and run a delegate?
If there is only the github readme available, what are typical values for database name, username, password, running port etc. mentoned there

Devs are on it.

Just join the blockpool discord channel , i uploaded a simple guide their on how to set up a node.

Yup , one vote cost you one BPL.
You can only vote one delegate per account/BPL address.

I voted for cryptooz_pool and I am very happy with this pool. The explorer site of this pool is very complete and I always see my BPL increasing!