How to fetch data when click for button?

Frappe Framework Customization
1

Hello everyone
Can someone give me steps for create button in my document ,and when click for that button can fetch drug table from patient encounter to current document
like this6253d192636670b6513b1be3aa5dd560e532ebca_2_690x364

2

frappe.run_serially([
() => frappe.timeout(1),
() => cur_frm.doc.field_name_in_new_doc = frm.doc.fieldname_in_prev_doc
])