Using wireshark
Wireshark doesn't support isolating traffic for a specific app.
You would have to close every other app running on your OSX to reduce the noise.
Once you find the tcp stream created by the app you can right click on the packet and choose 'Follow TCP stream'.
One better way to do what you are trying to achieve with Wireshark is to setup a VM and run the app inside the VM. Then you can sniff all traffic coming out of the VM by sniffing the VM virtual network interface.
Using nettop
In my opinion wireshark is the wrong tool to do what you need.
On MacOSX there is a very helpful tool called nettop.
Open a Terminal and run nettop -P
to get a summary of all the traffic generated by each application currently running together with their pid,.
On my machine I have:
bytes_in bytes_out rx_dupe rx_ooo
[...]
Skype.27479 1831 KiB 1950 KiB 32 KiB 20 KiB
[...]
Then you take the pid of your app (27479 in this example) and run:
nettop -p 27479
and you will see where the app is connecting to:
Skype.27479 1836 KiB 1955 KiB 32 KiB 20 KiB
tcp4 192.168.0.46:49355<->91.190.219.46:12350 en0 Established 429 B 694 B 0 B 0 B
tcp4 192.168.0.46:56325<->52.229.169.31:443 en0 Established 421 KiB 205 KiB 29 KiB 20 KiB
tcp4 192.168.0.46:51753<->157.55.56.149:40016 en0 Established 140 KiB 377 KiB 281 B 0 B
tcp4 192.168.0.46:51751<->13.69.188.18:443 en0 Established 117 KiB 84 KiB 2968 B 0 B
You can furtherly restrict the traffic shown to match some rules, but I suggest that you don't: you might be surprised to discover how many apps do not rely just on http/https :)
Run man nettop
for more details