Everything to stack and configure a 3850 is in this link
Your question on BGP is too generic/vague to answer BGP can be configured multiple ways and depends on your requirements and design what you put in place
http://www.cisco.com/en/US/docs/switches/lan/catalyst3850/software/release/3.2_0_se/multibook/configuration_guide/b_consolidated_config_guide_3850_chapter_01100101.html#concept_6902CB41AF7F4732971131D3A29D350F