I have used: sudo apt install filename
This is the output:
Reading package lists… Done
Building dependency tree
Reading state information… Done
Note, selecting ‘webthings-gateway’ instead of ‘/home/pi/Downloads/webthings-gateway-raspbian-buster-arm.deb’
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
webthings-gateway : Depends: libc6 (>= 2.28) but 2.24-11+deb9u4 is to be installed
Depends: libnanomsg5 (>= 1.1.5) but it is not installable
Depends: nodejs (>= 10.0.0) but 8.11.1~dfsg-2~bpo9+1 is to be installed
Depends: python3 (>= 3.7.0) but 3.5.3-1 is to be installed
Recommends: arping but it is not going to be installed
Recommends: mosquitto but it is not going to be installed
Recommends: sqlite3 but it is not going to be installed
E: Unable to correct problems, you have held broken packages.