first i would read up on some basic setting passwords , host names etc or you will run into issues even with this config
You will need to put your linksys into bridge mode to allow the public ip be used on the 881 usually the f4 interface is set for wan access
This is what your linksys is in Cisco + a default route for all internet traffic to go out your public
conf t
int vlan 1
ip address 192.168.1.1 255.255.255.0
no shut
int fa4
ip address 197.155.64.234 255.255.255.252
no shut
ip dhcp pool 881
network 192.168.1.0 /24
domain-name cisco.com
dns-server 41.220.238.4 196.201.231.167
default-router 192.168.1.1
lease 1
ip dhcp excluded-address 192.168.1.1
ip route 0.0.0.0 0.0.0.0 197.155.64.233
Good luck