You can register with tachomaster and use tachomaster at home either as a single user or your own company, there`s a free trial period then after that you pay to use it, iirc its around £1 per week per driver card
Do you mean the full tachomaster software or the Tachomaster worker app?
As said If the full software then you need a reader and pay to use the service.
If you are talking about the worker app then you need to request from your employer to set it up for you to have a login. They will give you a username and you will need to supply a 4 digit pin for them to set it up. Then once it’s set up you can log in and see limited info like WTD, Shifts worked, driving hours etc and infringements.