Use the interface eth0 (-i eth0) under promiscuous mode (-p) and save the result to the file (-o /tmp/p0f.log):

root @ kali:？ #p0f -i eth0 -p -o /tmp/p0f.log

-p0f 3.09b by Michal Zalewski

[+] Close 1 file descriptors.

[+] 322 signatures from' /etc/p0f/p0f.fp'.

[+] Intercept traffic on interface "eth0".

[+] Configure default packet filtering [+ VLAN].

[+] The log file "/tmp/p0f.log" has been opened for writing.

[+] Enter the main event loop.

. -[ 192. 168. 1. 15/35834->； 173 . 246 . 39 . 185/873(syn)]-

|

| client = 192. 168. 1. 15/35834

| os = Linux 3. 1 1 and later.

| dist = 0

| params = none

| raw _ SIG = 4:64+0:0: 1460:MSS * 20，7:mss，sok，ts，nop，ws:df，id +:0

In addition, I suggest reading the book "This is how Linux should learn" and getting familiar with the commands.