Get users who flagged a node

i saw handbook notes first (drupal.org/node/326308)
but there is one thing i am interesting in, it says:

"If your view work correctly, you can easily turn it into a block. Add a "Block" display. Since blocks don't get arguments from the URL, you'll have to add the "Node ID from URL" default argument. Lastly, enable your block (via "Administer >> Site building >> Blocks")."

especially the part

you'll have to add the "Node ID from URL" default argument

what is this from URL ? when i click on argument Node ID (it actually Node: Nid) how can i setup this?
Action to take if argument is not present:
Display all values (i suppose)

Validator:
?
flaggable node ?
faggable user ?

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there is another thing
on the handbook it says that we have 2 options:
1)

   1. Start a user-type view (as opposed to a node-type view).
   2. Add the "User: Name" field.
   3. Bring in the "Flags: User's flagged content" relationship. This step will link each user with all the nodes she has flagged (To be exact, not with her nodes but with her flaggings). By itself, this step is not very useful; so the next step is:
   4. Use the "Flags: Content ID" argument to filter the nodes (to filter the flaggings, to be exact) to the one having the node ID mentioned in the URL. You may set your page URL to, for example, node/%/who and make it a tab.
   5. You may wish to add the "Flags: Flagged time" field to show, besides each user, the date she bookmarked the node. You may then style your view as a table and make it sortable by either user name or flagging time.

2)

   1. Start a node-type view.
   2. Add the "Node: Nid" argument to filter the nodes to the one having the node ID mentioned in the URL. You may set your page URL to, for example, node/%/who and make it a tab.
   3. Bring in the desired "Flags: Node flag" relationship.
   4. Bring in the "Flags: User" relationship.
   5. Add the "User: Name" field. Associate it with the flag relationship.
   6. Here, too, you may wish to add the "Flags: Flagged time" field to show, besides each user, the date she bookmarked the node.

BUT !!
if you consider BLOCK
If your view work correctly, you can easily turn it into a block. Add a "Block" display. Since blocks don't get arguments from the URL, you'll have to add the "Node ID from URL" default argument. Lastly, enable your block (via "Administer >> Site building >> Blocks").

you cannot go for option 1 because in user-type view in Arguments we dont have option Node : Nid
so we go to option 2
we set up view (default) we add
1)relationship:
Flags: ownit by any user
(flag) Flags: User
2) Arguments:
Node: Nid
3) Fields:
(Flag user) User: Name
(flag) Flags: Flagged time

and know we want this in block right?
so we need this argument "Node ID from URL" but We already have it !? or dont we?
is this "Node ID from URL" = Node: Nid

or i should add bock display and add another node: nid

it is confuzing and it is not working !!! please tell me what i am doing wrong