DELFTship Version 7 does indeed require OpenGL version 3 or above. OpenGL should be part of your graphics adapter driver. Modern adapters (produced after 2008) normally support this, although a driver update may be necessary. Device drivers can be updated via the windows Device Manager. Alternatively you can download the latest driver from the website of your specific adapter.
If your adapter doesn’t support OpenGL 3+, then I recommend you try out DELFTship V6, also available from the software download area