Same way as normal boots ? Wear them for 20 mins to identify where they hurt your feet. Big fabric plasters on those bits of your feet. Thickish pair of socks and wear them around the house for a few hours at a time, gradually building up.
(scans post quickly for unintentional double-entendre, is satisfied)
I have a mighty fine pair of cowboy boots, but mine are black high-heeled and snakeskin with loads of metal studs so more of a goth-cowgirl hybrid.
And for the record, cowboy boots are cool, always have been cool, always will be cool. Except in the 80s when they became fashionable.