(very) General steps:
1) show route - shows you the interfaces and allows you to figure out where your traffic would go through
2) show run access-group - shows you what access list is applied to the interface(s) you identified in step 1
3) config t - enter configuration mode
4) access-list <access_list_name_from_step2> extended deny <tcp or udp> any any eq 8080
5) Test to see that you're blocking
6) wr mem - saves the config so it's not lost on the next reboot.
If you don't have access lists assigned via the access-group commands yet feel free to write back and we can help you get that part setup too... hopefully that's already done though.