First, you need to come up with a hypothesis.
NGS or microarray data can be obtained in SRA, GEO or ArrayExpress that can be used for expression analysis.
DNA data can be used for variation studies and RNA data in expression studies.
If you understand coding or these kind of analysis, I recommend you to use https://usegalaxy.org. But as Sandeep says you definitely need a hypothesis to test. After that based on your need, there are tons of R packages to help you to evaluate your data.