All interaction with a remote COM server is done via its interface pointers and the most common way to obtain the first interface pointer is using the function create-instance. This takes the CLSID of the server and returns an interface pointer for the i-unknown interface unless another interface name is specified.
For example, the following will create an instance of Microsoft Word:
(create-instance "000209FF-0000-0000-C000-000000000046")