Sounds like you are doing a good job so far.
So as far as play names go; this may depend on how complicated/what exactly you want to do.
Is it just once off data? Like the players enter their name but the game forgets next time it opens? Or is it more complicated with saved profiles and saved high scores which persist between plays?
To keep data between plays you will need to look up how to save database like files. I think they even use XML and similar. It's the same kind of thing you use to make complicated game saves, although simple high scores and profiles would be much easier.
However for the most simple form, with once off names used for display only in one game, the first step is to consider the game logic of how the player(s) will choose how many are actually playing- so it doesn't ask for 8 names when only 4 people are playing.
Next (for the simply still) you will need to rig up something that watches for any key stroke and records it. The variable for text is called a "String" (keep that in mind for searching for tutorials).
I did a mega quick search for "Playmaker text variable" (because "String" evaded my mind at the time) and easily found results in Google. Here is one:
https://www.youtube.com/watch?v=r2dJMp1QDRMI didn't really watch it so don't know if it has everything you need, but it does seem to show you the starting point of how you can watch the key strokes and do something with them. Does seem to be one of those silent + wave the mouse cursor ones, but yeah, may be helpful anyway.
Once you have saved some inputs as String variables then you simply do a Set Property for Text Mesh Pro (free). You select the actual component itself (not the gameobject for it) and then select.. um... I forgot. Maybe just "text" or something like that. Scroll down a little, the option is fairly obvious when you see it. Use it to set the text to be what the String is. I saw somewhere on this forum someone actually made a custom action set for Playmaker and Text Mesh Pro, but the built in Set Property still works.
You may need to *lock the FSM* to do this, as when you click on the text's gameobject you will see it open a new (probably blank) FSM. There is a little lock button on the FSM window so it will stay on that FSM no matter what gameobject you click (allowing you to click another object and see it's components to drag into an action).
Maybe for simplicity sake have all 8 text objects positioned in your UI, but start them with no text (blank) and so can use the Strings to set them to something otherwise you wont' know they are even there.
And yeah, if you didn't already know, built in Unity text is garbage. Use Text Mesh Pro (free version) or something else or all you will get is jaggy terrible text.