Unfortunately Frontpage Extensions can not be installed automatically, it must be installed manually. Follow the below steps to install Frontpage manually.
Login to Plesk server as admin.
Run the package installer to install the application using the MS Frontpage server extensions distribution package which you obtained.
Go to settings and select Server components. You can view the list of components there. Click refresh to refresh the component list then the integrated component will appear in the list.
If you want to upgrade it, obtain the upgrade package of MS Frontpage and apply the upgrade to the existing installation.
Follow the general integration procedure as in step 3. That's all.