Summarize the following:
After you have successfully created a Party, you can now start inviting people. One way to invite members is sending invitation through your friend's list. To do this, open your Friend List window by pressing Alt+H. Right-click on the name (player must be online) and then choose “Invite to Join Party.” This is the most common way to invite people in your party. Meeting up in the game is convenient for players who are searching for party in a certain area, such as in Al De Baran and Glast Heim, since most players prefer to search for party and then enter the field right away to hunt. All you have to do is meet up with your friend or with people who wishes to join your party, right-click their character and then choose “Invite to Join Party. Similar to inviting people using your friend's list, you have to open your Guild list first by pressing Alt+G and then search for the name of the player in member's list. Right-click on the name and then choose “Invite to Join Party” to send them an invitation.  You can invite up to 12 people in 1 party. Remember that there's a level gap. Each member should be within the 10 level difference to have the EXP Even Share work. Otherwise, the EXP Even Share won't be available in the party setting.

Summary:
Invite through Friend's list. Meet to Invite. Invite through Guild list.