how to put an indent of 0.5in in apa7

I use the standard apa7 to write my essay but I don’t know how to indent each paragraph.
Can somebody help me?
here is the preamble I use for the full document (math document)

documentclass[a4paper,man,floatsintext]{apa7}
usepackage[american]{babel}
usepackage{amssymb,amsthm,mathtools}
usepackage[T1]{fontenc}
usepackage[utf8]{inputenc}
usepackage{fancybox}
usepackage{graphicx,float}
usepackage{booktabs,tabularx}
usepackage{caption,subcaption}
usepackage{algorithmicx}
usepackage[ruled]{algorithm}
usepackage{algpseudocode}
usepackage{xcolor}
usepackage{csquotes}
usepackage[backend=biber,style=apa]{biblatex}
usepackage{tikz}
usepackage{pgfplots}
usepackage{pdfsync}
usepackage{hyperref}

DeclarePairedDelimiter{norm}{lVert}{rVert}
setcounter{secnumdepth}{77}
setcounter{tocdepth}{77}
newtheorem{rem}{Remark}[section]
newtheorem{defi}{Definition}[section]
addbibresource{C:/Users/Charriffaini/Documents/latex/distbib.bib}
fancyhead[l]{}

begin{document}
The biological clock functions regardless of the normal
24-hour cycle of light and darkness. Light is involved in
resetting and regulating the clock.


The biological clock functions depend on the normal 24-hour cycle of light and darkness regarding its resetting and regulating.
Although the biological clock functions on the normal 24-hour cycle of light and darkness, light is still involved in resetting and regulating the clock.
end{document}

Instead of this small text, I used separated files which I took them in by the following intruction

include{chapter}

After the compilation, none of the paragraph is indent.

setlength{parindent}{0.5in}