Hi! To let a switch port (logical or physical) be an untagged (or tagged -> change untagged with tagged) member of a particular VLAN id you should enter into - in config mode - the particular VLAN id context with the vlan <vlanid> CLI command and, once in that VLAN context, perform the untagged <portid> CLI command (where the <portid> is the identifier of the particular port you're working with).
Alternatively you can issue the command directly against the physical/logical interface - always in config mode - with the interface ethernet <portid> untagged vlan <vlanid> CLI command.
An access port generally means that a port is untagged member of a particular VLAN id (default is 1) and that is connected to a host VLAN unaware (where VLAN id is not set).