Please have a look at the following resources:
- ESA notes on radar interferometry: http://www.esa.int/esapub/tm/tm19/TM-19_ptA.pdf
- ESA notes on the selection of suitable images: http://www.esa.int/esapub/tm/tm19/TM-19_ptB.pdf (chapter 1.3 Selecting images for InSAR DEM generation)
- ESA tutorials on displacement:
Sentinel-1 TOPS interferometry
InSAR Displacement mapping with ERS data - This video on downloading Sentinel-1 data from the copernicus hub: https://www.youtube.com/watch?v=AFXfh7zCBxY
- This topic on displacement mapping in SNAP Subsidence map in 3d view
If you struggle at a specific point, feel free to ask in the mentioned topic. But please bring some patience to understand all the things behind this analysis. This is nothing to master overnight 