Here is a quick tip on how to create the email signature and use it in Dynamics 365 CE.
Below are the steps to create the email signature.
Goto Settings > Templates > Email Signatures
Click on new button to create new email signature
Enter your signature and click on save & close
Now, you will be able to see your email signature as below.
Next, I will show you how to insert the signature in email.
Goto Activities -> Click on New email
Please provide the subject and email content. Once you are done click on Insert Signature as below.
Please select the required email signature from the list.
Now you will be able to see your signature in your email.
I hope this blog post helps you. If you are interested to know more on this topic then, I encourage you to check out my blog on this.