Via the stats through skills mod? Every 3rd, 6th, and 9th skill level raises the relevant stat by 1.
grabs the lua file to find what skills do what
--Str based skills
str_bonus = calc_bonus(str_bonus,"carpentry")
str_bonus = calc_bonus(str_bonus,"mechanics")
str_bonus = calc_bonus(str_bonus,"swimming")
str_bonus = calc_bonus(str_bonus,"bashing")
str_bonus = calc_bonus(str_bonus,"cutting")
str_bonus = calc_bonus(str_bonus,"melee")
str_bonus = calc_bonus(str_bonus,"throw")
--Dex based skills
dex_bonus = calc_bonus(dex_bonus,"driving")
dex_bonus = calc_bonus(dex_bonus,"survival")
dex_bonus = calc_bonus(dex_bonus,"tailor")
dex_bonus = calc_bonus(dex_bonus,"traps")
dex_bonus = calc_bonus(dex_bonus,"dodge")
dex_bonus = calc_bonus(dex_bonus,"stabbing")
dex_bonus = calc_bonus(dex_bonus,"unarmed")
--Int based skills
int_bonus = calc_bonus(int_bonus,"barter")
int_bonus = calc_bonus(int_bonus,"computer")
int_bonus = calc_bonus(int_bonus,"cooking")
int_bonus = calc_bonus(int_bonus,"electronics")
int_bonus = calc_bonus(int_bonus,"fabrication")
int_bonus = calc_bonus(int_bonus,"firstaid")
int_bonus = calc_bonus(int_bonus,"speech")
--Per based skills
per_bonus = calc_bonus(per_bonus,"archery")
per_bonus = calc_bonus(per_bonus,"gun")
per_bonus = calc_bonus(per_bonus,"launcher")
per_bonus = calc_bonus(per_bonus,"pistol")
per_bonus = calc_bonus(per_bonus,"rifle")
per_bonus = calc_bonus(per_bonus,"shotgun")
per_bonus = calc_bonus(per_bonus,"smg")