Only the Guild Master and Assistant Guild Master has right to accept to applicants.
If the applicant is nearby right click on the character and click Guild Invitation.
If the applicant is not around, type in '/invite character's name' command in the chat window to send an Invitation. A pop up menu will appear on the user who received an invitation and if the user accepts the invitation, the user is automatically registered as a member of a Guild.

Right click on the Character Stats window placed in top left corner of the screen with the mouse, and withdrawal menu appears. Or type in '/withdraw' command in the cat window to withdraw from a guild.

Withdraw/Ban : There are no penalty for withdraw or ban from a guild and the user can join other Guild instantly. Only the Guild Master can request for Disband of a Guild and it takes 7days to complete the procedure upon request. The guild master can create another Guild after 17 days from the disband of a Guild.