To view step by step guides for the various email platforms, please visit the following links
Outlook (Desktop): https://signature.email/guides/how-to-add-signature-in-outlook
Outlook (Online): https://signature.email/guides/how-to-add-signature-in-outlook-online
iPhone Default Mail App: https://signature.email/guides/how-to-add-signature-on-iphone
For all others: https://signature.email/guides