Write text with Proxmark3 Easy

Sorry, Your thread title even mentions what you are wanting to do, It looks like I am the one struggling with English.

Anyway, You can certainly do it.
You will need to write line by line on the blocks

To learn, I would reccomend you use an app to write the data you want on your NExT as an example, Then,

Use
NFC Tools
“Read” - Record 1- Details…

BUT TagInfo will be much easier to understand the output, so If you do a scan with TagInfo, and look at the “Full Scan” - Memory content

That is basically what you need to replicate. including the syntax, format and which blocks, you can and also shouldnt write to.

I cant help you much more as I don’t have a Proxmark with me at the moment, so I would only be able to guess the commands
If you look in the menus from

hf 14a

Whatever you do, I would strongly reccomend you practice on a card/fob and NOT on your NExT

Hopefully somebody will be along shortly to give you some more specific commands