Lots of great advice above.
Another hint to get a large number of symbols and footprints on your drawings is to use the “duplicate” function.
Place a resistor symbol on your page and associate it with a footprint.
Duplicate that symbol, highlight both symbols by enclosing them in a box, duplicate. Highlight all four with a box, Duplicate. Highlight all eight with a box, duplicate.
You now have 16 resistors, all with different Refs. but all with the same footprint.
This works with most everything.
Highlight all 5 parts of a 74xx IC and duplicate. You now have 2 complete ICs.
With regards to your Kicad libraries, download and install all of them and hide the ones you do not need. One day you will need them, particularly the footprints.
You will also need personal libraries for imported or DIY symbols and footprints.
The “Getting Started” doc. is great. I also wrote this FAQ to help newbees with library creation and management.
Just to complete answering this question: look up the data sheet for the part on the internet.
You will find in that data sheet, all the various packages available for that component. Decide on the package you need/want and find it in the Kicad footprint libraries.
eg. A 74HC00 is available in all these packages:
Now go through the various “Package” libraries in Kicad footprints to find the footprint you need.
A hint: Kicad knows all five parts are in the one package, so when you place a footprint on one gate, that footprint will automagically be placed on all the other parts of that symbol.