First, if you are going to run BGP you will need to check with your provider first. Since you have an ADSL my guess it they will not peer with you.
However, if you want to run basic static route that can be done.
You need to make sure you have the correct card in your router to accept the ADSL connection.
Info you will need from your ISP
IP address. You will need to know the IP they are assigning, request static so you don't have to change anything. You could use DHCP but if they offer static I would use that.
Basic config:
To get you connected, not specific to your type of connection or interfaces, this is just to be used as a guide.
interface Ethernet 0
description Connected to Local LAN
ip address x.x.x.x 255.255.255.x <---IP the ISP provides, unless you are going to run NAT, then you would configure with private IP.
no shutdown
!
interface Serial 0
ip unnumbered ethernet 0
no shut
!
ip route 0.0.0.0 0.0.0.0 serial 0
another config option
interface FastEthernet0/0
ip address x.x.x.x 255.255.255.0 <---whatever IP you assign in the private range
!
interface Serial0
description Connected to ISP
ip address x.x.x.x 255.255.255.252 <--IP provided by ISP
!
ip route 0.0.0.0 0.0.0.0 Serial0
This should help get you started.
For NAT:
In global config:
ip access-list extended nat_inside
permit ip x.x.x.x 0.0.0.255 any
(this is the IP subnet you apply to the ethernet interface)
!
ip nat inside source list nat_inside interface Serial0 overload
!
apply this to the serial interface
!
ip nat outside
!
This should help get started with a basic NAT config.
