The payment request is the way to go to send your customers a bitcoin address from your Electrum wallet.  The amount is not important - you could set the amount to 0.00 BTC and let the sender decide how much to send in the future. A new Bitcoin address from the list of available addresses will be used (not created) for every payment request.  Electrum generates automatically bitcoin addresses - deterministically - based on the Master Private Key (which is derived from the wallet seed words).  All the keys in the Electrum wallet are a child of that Master Private Key - as you use them, new "child" keys are revealed automatically by Electrum (how many unused addresses are revealed at the same time depends on your gap limit setting).  

Don't worry about the "expiration" of the request either, Bitcoin addresses don't expire - addresses are representations of public keys.  To be confirmed, but I believe this locks the Bitcoin address from being used by Electrum in another payment request, until the expiration time is over (in case the customer didn't use it).  I would make the address available again in the pool of "new" addresses, if unused during the time period.

The instructions link presented above would be the right way to do it, other than that you can manually create an address, label it to that user's name and allot it to their account.

Yes, I was lost in translation, I think he is just looking a way to assign address to people's accounts who register on his site and so when they send money to that address it will show up in their account, kind of like when you register on a gambling website, you get a deposit address and any money sent to that get added to your account.

Twister didn't get your question as should be I suppose .
So yes you can do , see the documentation here : http://docs.electrum.org/en/latest/merchant.html

electrum addrequest 3.14 -m "this is a test"