Co-registration of Sentinel-1

Dear ABraun,
I use this topic to show my problem with coregistration and I am sure you can help me with that.
I am having a problem with coregistration of a time series of GRD products.
My work flow is:

  1. Subset data
  2. Apply orbit file
  3. Remove Thermal Noise
  4. Calibration
  5. Create stack
  6. Multispeckle
  7. Terrain Correction
  8. Linear to dB

Now, I would like to apply the coregistration step, but the tool asks for two input data and I have only one as a stack.
How can I do that? For the time series analysis, the only “create stack” is enough for it or it is necessary to coregister all the datasets?
Thank you in advance for your help.

Salvatore