How to extend oracle database to a newly added hard disk
As beginner, I strongly recommend to start working with the classical way on filesystems.
Then you must be aware, where do you need more capacity within your database.
Ensure, that the new disk is available on OS. Then go ahead with following hints and steps:
(Very high level, simple and the classic way)

Users can create objects (Tables, Indexes, Views, Procedures, Sequence, ...)
Objects, which are storing any kind of data are segments, e.g. tables/indexes.
Each table is always stored within only one Tablespace.
Users can locate different tables/indexes etc. into different Tablespaces.
Tablespaces consist of one or more datafiles.
A DBA can add as many datafiles to a tablespace as he likes (ALTER TABLESPACE ADD DATAFILE).
Each new datafile enlarges the capacity of only this tablespace.

To answer your question, you need to know, which tablespace needs the additional space. Then you can add a new datafile with command above (there are tons of examples) and locate the datafile to the mountpoint of your new disk.
If you are new, you should start with a database on standard filesystems and play around with datafiles. Other options like ASM are not a good starting point for beginners, if you want to learn.