First install openssl in your windows, then open make environment variable of it so that openssl is accessible at any path of cmd

To generate pfx file from crt you need 2 files, better if these 2 are at same path

1- .crt file

2- .key file (provate key)

in cmd go to path of .key & .crt file and run below command, update .key & .crt file names if needed

Import pfx in IIS

Go to IIS, click root server at left side,

then click server certificates

click import from right pane

browse .pfx file and type in pfx password

click import

not go to website right click and then click bindings

see if 443 is there then update it else add new binding and add certificate to it