device(config)# router bgp device(config-bgp-router)# address-family ipv4 unicast device(config-bgp-ipv4u)#

Note
The commands that are available from the address-family IPv4 unicast configuration level are also available from the address-family IPv6 unicast configuration level. Each configuration level allows you to access commands that apply only to that particular address family.
device(config-bgp-router)# address-family ipv4 unicast
device(config-bgp-ipv4u)# ?
Possible completions:
aggregate-address Configure BGP aggregate entries
always-propagate Allow readvertisement of best BGP routes not
in IP Forwarding table
bgp-redistribute-internal Allow redistribution of iBGP routes into IGPs
client-to-client-reflection Configure client to client route reflection
dampening Enable route-flap dampening
default-information-originate Originate Default Information
default-metric Set metric of redistributed routes
graceful-restart Enables the BGP graceful restart capability
maximum-paths Forward packets over multiple paths
multipath Enable multipath for ibgp or ebgp neighbors
only
neighbor Specify a neighbor router
network Specify a network to announce via BGP
next-hop-enable-default Enable default route for BGP next-hop lookup
next-hop-mpls Changes for IPoMPLS route download, pkt path.
next-hop-recursion Perform next-hop recursive lookup for BGP
route
redistribute Redistribute information from another
routing protocol
rib-route-limit Limit BGP rib count in routing table
static-network Special network that do not depends on IGP
and always treat as best route in BGP
table-map Map external entry attributes into routing
table
update-time Configure igp route update interval