Check your login profile.  It is probably set to Basic Mode.  In Basic Mode, certain options deemed to be more advanced do not appear.  Site administrators and list owners who are comfortable with the full set of LISTSERV options are encouraged to set their login profile to Expert Mode, in which all options will appear in the wizards.  Depending on your LISTSERV version, this is set in one of two ways:

In LISTSERV 16.0 and 16.5, the user mode is set by clicking Preferences on the toolbar, then choosing the General Preferences tab (which should display by default).  Change the Mode preference by choosing "Expert Mode" in the drop-down box.  Then click the Update button at either the top or bottom right of the Preferences page.  NOTE:  You may have to log out and log back in before the new preference becomes active.

In LISTSERV 17.0 and later, the user mode is set by clicking on your email address at top right, then clicking the Edit Profile button in the pop-up window.  This opens the Edit Profile dialog, where you can set the Mode by choosing the appropriate value from the drop-down box.  Choose "Expert Mode" and then click Save.  This will set the display mode and the page you are looking at will reload with all options visible.

If you are already set to Expert Mode:

Are you running LISTSERV Lite?  In LISTSERV Lite, some options are not available and will not be displayed in the configuration wizards.  Check the appropriate documentation for the setting you wish to change -- if a particular setting is not available in LISTSERV Lite, there will be a note to that effect.

Otherwise, try logging out and logging back in to clear the LISTSERV login cookie stored in your browser.  In extreme cases you may have to clear your browser cache.