1. Install LaTex

sudo apt install texlive-full

2. Install TexStudio

sudo apt install texstudio

3. Set up TexStudio

Basic setting

Options > Configure TexStudio > Click Show Advanced Options
(a) > Go to Adv. Editor > Unclick Auto Complete Parentheses
(b) > Go to Editor > Select Ignore Indentation in Indentation Mode

Macro Setting

Macros > Edit Macros

Then, copy the follwoing

%SCRIPT
txt = cursor.selectedText() 
editor.write("\\mathbf{"+txt+"}") 
cursor.clearSelection()

Using this, you can apply mathbf by Shift + F1.