These files are all found in the hadoop/conf directory.
For setting HDFS you have to configure core-site.xml and hdfs-site.xml.
HDFS works in two modes: distributed (multi-node cluster) and pseudo-distributed (cluster of one single machine).
For the pseudo-distributed mode you have to configure:
In core-site.xml:
<!-- namenode -->
<property>
<name>fs.default.name</name>
<value>hdfs://localhost:8020</value>
</property>
In hdfs-site.xml:
<-- storage directories for HDFS - the hadoop.tmp.dir property, whose default is /tmp/hadoop-${user.name} -->
<property>
<name>hadoop.tmp.dir</name>
<value>/your-dir/</value>
</property>
Each property has its hardcoded default value.
Please remember to set ssh password-less login for hadoop user before starting HDFS.
P.S.
It you download Hadoop from Apache, you can consider switching to a Hadoop distribution:
Cloudera's CDH, HortonWorks or MapR.
If you install Cloudera CDH or Hortonworks HDP you will find the files in /etc/hadoop/conf/.