For connectors simply use the conn_RRxPP symbols from conn.lib? (RR= number of rows, PP = number of pins per row)
Maybe there is a connector symbol in the conn list that you like more.
Or draw up your own symbol if you do not like any of the symbols available.
This symbol is then assigned a footprint.
Either place a wire solder connector if you have a short wire to connect to the chassis connector or design the footprint for your chassis connector if it is placed directly on the pcb. (This is what you really might need to design your self. In most cases it takes longer to find a suitable footprint then to draw one.)
I have the feeling you do not yet understand what symbols are. In kicad there is no real concept of a component. There are symbols and footprints (and 3d models but they are unimportant here)
What are symbols
A symbol is an abstracted representation of the function of your component. At least it needs to have the pins that are present in your component. (Artwork is necessary for the reader of your schematic. There are a few standards that define how symbols should look like.)
What is a footprint
A footprint represents the landing pattern of a component. (This is most likely given somewhere at the end of the datasheet of your component.)
It at least needs to contain all the connection points (called pads) to solder the component to. (Shape and size/ position of the pad should align with what is given in the datasheet.)
Pads define stuff on copper, mask and paste layer (copper is the area that is covered by copper. mask gives the cutout in the solder mask layer, past is the cutout of the solderpaste stencil used for reflow soldering.)
It should also contain an outline of the component such that the designer knows where they can not place other compoents. (courtyard)
It is beneficial if it also contains an outline and pin 1 marker on silk for soldering/debuging.
Artwork on the fab layer is beneficial if you want to document your board.
Connecting symbol to footprint
In kicad the connection is done via the pin number given to the pins in the symbol and the pin number given to the pads in the footprint.
The second part of the connection is made via the footprint field of the symbol.
This field can be set either when creating the symbol (we call such symbols atomic) or lather when it is already placed in eeschema. (generic symbols)
For generic symbols there are two ways to select the footprint. Either via the symbol properties dialog/footprint browser or via cvpcb.
(cvpcb can be used to set the footprint fields of all used symbols at once.)