How to standardise NaOH?
You should find it in any analytic chemistry textbook, considering volumetric methods. 
We did so in the high school.

In short, a solution of known molar concentration of well defined acidic substance is made, that get titrated by the $\ce{NaOH}$ solution.

Typically oxalic acid $\ce{(COOH)_2 . 2 H2O}$, weighted at good scales, preparing solution $\pu{0.05 mol / l}$.

When you Google "acidimetric titration sodium hydroxide oxalic acid" , you get tons of references, from illustrating videos to PDF documents.