In addition to using the software in the classroom it can also be used at home, below are some simple instruction to help you out.
To access purple mash you need to go via the main IPACA website. Once here along the top menu there is a tab that says purple mash - click this link
You will then arrive at a log in page that looks like this:
This is where you need your children's log in details. All pupils took home 2 login cards the one you are looking for is the purple one, as shown below.
Currently purple mash isn't supported on tablets so will only work on laptops or desktop computers, hopefully in time this software will be supported on a range of tablets.