how do i get images from the web at 300dpi for printing

[FIERYFRANK]

help! i've just designed a backdrop to be made into a large pvc banner, but it can't be printed because its not 300dpi and the image 'explodes' at the size i want it to be. its a simple flag and text image....do i have to make sure that the flag image and the text font are 300dpi before i make a new photoshop document at 300dpi using the flag and text? if so, can anyone direct me to a site or sites where i can download a union flag and hel grotesk gothic font at default 300dpi? any help much appreciated!