Hi shrey, welcome.

1.) Normal that is done by pressing Ctrl+F3 (Shift+F3 for backwards)

BTW, It is enough to have the cursor on an word or sign.
No need to select something.
This works even for signs like “=” without selecting first.

2.) Since that is an kind of an search,
all other occurrences are highlighted too.

See “Tools > …Config.. > [Display] Search String” for settings.
And with “Search Colors [ 1]” you can even set to highlight
more then just the last search but the last two, or three, or…

3.) To remove that current highlighting from view, press Alt+F3.

Having the cursor somewhere inside of the word “sc|ript“.
Pressing now the key combination “Ctrl+F3”
will jump to the next occurrence of that word
AND search-highlight all occurrences of that word in the whole document.

Pressing “Shift+F3” jumps backwards to the last occurrence.
Pressing “Alt+F3” will remove the highlighting from view.

<script src='xxx/scripts/shCore.js'></script>
<script src='xxx/scripts/shBrushCpp.js'></script>
<script src='xxx/scripts/shBrushCSharp.js'></script>


BTW: to highlight some words on demand, you may want
to take an look at MARKERS > http://www.emeditor.com/modules/feature1/rewrite/tc_39.html