Perhaps you can start from here.
If you are using the latest version from GitHub:
\renewpagestyle{scrheadings}{%
{\smash{\hspace{-\headmarginparwidth}\hspace{-\headmarginparsep}\makebox[\headtotal][l]{%
\makebox[7\hscale][r]{\thepage}%
\makebox[3\hscale]{}\rule[-1mm]{0.5pt}{19\vscale-1mm}\makebox[3\hscale]{}%
\makebox[\headtextwidth][l]{\leftmark}}}}%
{\smash{\makebox[0pt][l]{\makebox[\headtotal][r]{%
\makebox[\headtextwidth][r]{\hfill\rightmark}%
\makebox[3\hscale]{}\rule[-1mm]{0.5pt}{19\vscale-1mm}\makebox[3\hscale]{}%
\makebox[7\hscale][l]{\thepage}}}}}%
{\smash{\makebox[0pt][l]{\makebox[\headtotal][r]{%
\makebox[\headtextwidth][r]{\hfill\rightmark}%
\makebox[3\hscale]{}\rule[-1mm]{0.5pt}{19\vscale-1mm}\makebox[3\hscale]{}%
\makebox[7\hscale][l]{\thepage}}}}}%
}{%
{\hspace{\dimexpr -\headmarginparwidth -\headmarginparsep}\makebox[\headtotal][l]{%
\makebox[\textwidth][l]{F-in-JAR}%
}}%
{\makebox[0pt][l]{\makebox[\headtotal][r]{%
\makebox[\headtextwidth][r]{\hfill F-in-JAR}%
}}}%
{\makebox[0pt][l]{\makebox[\headtotal][r]{%
\makebox[\headtextwidth][r]{\hfill F-in-JAR}%
}}}%
}
If you are using the template on Overleaf from latextemplates.com:
\renewpagestyle{scrheadings}{%
{\hspace{-\marginparwidth}\hspace{-\marginparsep}\makebox[\overflowingheadlen][l]{%
\parbox[t][1.7cm][c]{2em}{\hfill\thepage}%
\makebox[2em][c]{\rule[-1.03cm]{1pt}{1.55cm}}%
\parbox[t][1.7cm][c]{\textwidth}{\leftmark}}}%
{\makebox[\overflowingheadlen][r]{%
\parbox[t][1.7cm][c]{\textwidth}{\hfill\rightmark}%
\makebox[2em][c]{\rule[-1.03cm]{1pt}{1.55cm}}%
\parbox[t][1.7cm][c]{2em}{\thepage}}}%
{\makebox[\overflowingheadlen][r]{%
\parbox[t][1.7cm][c]{\textwidth}{\hfill\rightmark}%
\makebox[2em][c]{\rule[-1.03cm]{1pt}{1.55cm}}%
\parbox[t][1.7cm][c]{2em}{\thepage}}}%
}{%
{\hspace{\dimexpr -\marginparwidth -\marginparsep}\makebox[\overflowingheadlen][l]{%
\makebox[\textwidth][l]{F-in-JAR}%
}}%
{\makebox[0pt][l]{\makebox[\overflowingheadlen][r]{%
\makebox[\textwidth][r]{\hfill F-in-JAR}%
}}}%
{\makebox[0pt][l]{\makebox[\overflowingheadlen][r]{%
\makebox[\textwidth][r]{\hfill F-in-JAR}%
}}}%
}
It will print F-in-JAR in the footer of every page.