You start off by creating the account itself; will also create a user if you do not already have one. You can create an account here create_account.aspx
The create account page will trigger an e-mail to you with a link you would need to use to activate your user (and account).

When you have activated your user and you are signed in - use the "Invite" functionality in the top right menu to add users to your newly created account; will send an invitation e-mail to the once you invite.

Creating a user gives you access to all the services created for individuals like Digital Twin (Smart CV), Tests (IQ, Personality etc.), Simulations, Games, Indexes, Advisory services and soon to come Friends recruiting

When creating an account you get access to all the individual services pluss more advanced services like Projects (recruting, assessments, readiness) and Job Profiles; you also get admin. and config tools for account-users and associated advanced services.

Users are for free, while Accounts are payable - see https://talection.com/productprice.aspx for details.

Yes you can. Creating an individual user is for free and can be used as such for as long as you want.
An Account subscription is payable, but you can create one now and try it out for free.