Packages are groups of functions. You can't use a function until it has been both installed and loaded (or else R won't recognize the function name).
Create an object (or change the value) by using the arrow pointing toward the name you are giving your object (type a less than sign "<", then a dash "-"). The "type" of your new object will depend on what is on the right of the arrow. To print the contents of your object, just type the name of the object.
For objects of type list or dataframe, you can get specific parts of the object using brackets or dollar signs.
There are 4 basic concepts you need to understand: