To get the weight of glucose to be dissolved in solvent (usually water), first you must do the following computations:
(1) Convert the given volume from milliliters (mL) to liters (L).
(2) Convert the given number of Liters to number of moles (mol) using the given molar concentration (unit is moles per Liter solution).
(3) Convert computed number of moles to number of grams (g) using the molecular weight of the substance.
Therefore, in order to get a 0.05 molar solution, you must dissolve 2.25 grams of glucose in 250 milliliters solvent.
Here is a video that explains in details how to prepare a solution in the lab:
Lab Demonstration | Solution Preparation & Dilution.