SQL & PL/SQL :: INSERT Data Into Database

I have a question how to do this.

I'm using JAVA class. I'm try to put "data" to database(INSERT data to database - PL/SQL).

I have simple JDBC problem:

Steps.
1) SELECT table_seq.NEXTVAL FROM DUAL;
(Question: How can I make sequence to table ? I see lot of examples on google but all is just to create sequence but not for table. Maybe sequence can be put on table ?)

2) INSERT table_seq.....

3) INSERT table (values) values ('data')

Tables look like this:

table1 [Where I need to take `id`]
------------
id .....
------------

table2 [Where I need this sequence to be taken]
------------
seq_id .....
------------

table2 [Where I need to put `seq_id` into table2.id and data]
------------
id data
------------

I don't get it why can't I just do this ?:
INSERT table2 (data) values ("this is data");