SELECT [field names go here, separated by commes] FROM [table name] WHERE [field name you want to compare] LIKE/= 'value to compare to field'
That'll spit out, say, all records where 'firstname' = 'John', etc. from there you basically just add on query params, unless you actually have to do joins and whatnot. also check w3schools. it might not be specific to using SQL in access, and is probably for MySQL, but the basics are pretty much the same, and if you're using access, i doubt you're doing anything more than the basics anyway. hope that helps!