E-contract- how to make an agreement between two parties who are geographically apart & work online

You can send them the agreed draft contract by eamil and they can printout the document and sign and stamp and send you by post. 

Or simply agree on elctronically signed doument

that is best option

Electronically you can sign by registering on docusign;

https://www.signnow.com/alternative/docusign-alternative-signnow?gad=1&gclid=EAIaIQobChMI1vvwmff2gAMVOYtoCR1W9ANAEAAYASAAEgIxo_D_BwE

cool that is really nice

Since digital signatures are legally valid worldwide and offer much better security than wet signatures, they have become an indispensable part of the contract lifecycle.

You may draft the agreement through a lawyer, exchange it with the customer, after the customer is okay with the mutually agreed conditions therein, then you can prepare the original agreement with digital signatures, and can exchange the same with the customer who will return the same with his digital signature by return email.

This will be easiest way to enter into the desired contract.