To install:
sudo python setup.py install

To run validate tool:
p4-validate <path_to_p4_program>

To open a Python shell with an HLIR instance accessible:
p4-shell <path_to_p4_program>

To build the HLIR and access its objects:
from p4_hlir.main import HLIR
h = HLIR(<path_to_p4_program>)
h.build()

You can then access the different P4 top level objects using these Python OrderedDict's:
h.p4_actions
h.p4_control_flows
h.p4_headers
h.p4_header_instances
h.p4_fields
h.p4_field_lists
h.p4_field_list_calculations
h.p4_parser_exceptions
h.p4_parse_value_sets
h.p4_parse_states
h.p4_counters
h.p4_meters
h.p4_registers
h.p4_nodes
h.p4_tables
h.p4_action_profiles
h.p4_action_selectors
h.p4_conditional_nodes

The ingress entry points are stored in a dictionary:
h.p4_ingress_ptr

The egress entry point is:
h.p4_egress_ptr

To access the P4 types you can use the following import:
import p4_hlir.hlir.p4 as p4