How exactly do you go about entering the mindscape? Well the solution isn't all that hard, a lot of people hype it up to be a extremely advanced topic, but I view it as one of the easier things to learn.
Now then..
Method 1 -
The first method would be link to the target, and then go to the location of there crown chakra, once you have found such, you are going to look into it, yes this doesn't make sense at first, but your goal is to "project" in to it, as that is normally the easiest method to find the mindscape.
Method 2 -
The next method I personally prefer is to simply scan the target and then keep digging deeper and deeper into them, if you do go far enough you will eventually stumble upon a area that appears to be a separate plane, and this would be the mindscape/soul landscape. (Which ever term you prefer).