Wireshark packet report

I manage a small client server network and the users are complaining about webpages loading slow.
Generally slow internet. I have narrowed this down to a device on the network that is uploading excessive data.
I can log in to the ISP customer data portal and run 5 minute data reports.
I have run Wireshark and I need the Packet report analysed by a trained eye as I am not sure of the results.
Basically I am looking for an IP address that is transmitting a lot of packets that is using up the upstream bandwidth. There service is an ADSL2+ 4704/384.
As you u can see their upstream bandwidth is limited so when the device transmits it uses all the bandwidth and slows the internet. How do I upload the packet report PCAPNG file? All help is greatly appreciated.