It works like always and as illustrated several times previously (appropriate consideration of instrumental broadening and other types of broadening). The particle size/layer thickness, of course, an upper limit of the column lenght which you actually determine upon applying the Scherrer equation.

Generally note: like with every experimental approach, application diffraction line profile analysis requires dealing with the basics of the approach and it is always dangerous to uncritically click at some keys using some software you do not understand. And the Scherrer equation is correct, but it is requires some (frequently described) careful steps upon application and careful interpretation of the outcome.