To build re-usable estimates for the whole clinic you'll go to Inventory Settings:
Then open up "Pre-built Estimates" and click the green "plus" button in the lower right corner:
From there you will build out the assessment the same way as if you were entering assessments and tests and treatments into an encounter record.
In order to build an estimate for a specific patient, go to the "Patient Context Menu" on the patient's dashboard and select "Build/Manage Estimates":
From there you'll click the "plus" button and get to the same screen as above (with the additional option of being able to choose to extend a clinic pre-built estimate if you'd like).