Adding a web part to a classic page
Go to the page where you want to add your web part and click Edit.

Open the Insert tab, find Web Part, and click it.
In the Categories list, select Virto Solutions, then select the Virto User Manager web part you want to embed on the page. Click Add.

Click the settings icon on the web part and select Edit Web Part.

Note: On SharePoint Server Subscription Edition, the tool pane for classic web parts is turned off by default. A farm administrator turns it on for a site collection with Enable-SPToolPane -Identity <site collection URL>.
In the tool pane, expand User Manager web part settings and click Configure WebPart. Until a fieldset is chosen, the web part shows “Configuration is not set for this Web Part”.

Choose the fieldset for the web part. Choose a fieldset made for this web part: the list shows all fieldsets. (For details on how to configure a fieldset, see the Settings section of this documentation.) Then click Save.

In the upper-right corner of the page, click Save again.

Now, the web part is ready to use.