The Plainlink code is used to edit the yellow description rectangular-box you can see if you hover with your mouse over a Link.
The code for Plainlinks is:
[[Link|<span style="plainlink" title="TEXT 2">TEXT </span>]]
That gives you:
Hover over the Link to see the Plainlink.
To use this code,
Linkwith the name of the page you want to go to,
TEXT 2with the text you want to have in the Plainlink,
TEXTwith the text your Link will have.