Is the disposable kit you bought at Walmart the prepackaged squeeze bottle type? Or is it a bag type that you fill with water based solution (such as soap or salt)?
If it is the prepackaged squeeze bottle type, my advice is to throw it away and buy yourself an enema bag. You can find them for under $15 for sure, possibly under $10. A hospital Fleet disposable enema bag is less than $5 and can be found in many medical supply stores, and some pharmacies. Almost any pharmacy can order one for you if they don't have it in stock.
Don't be concerned about your enemas, millions of people have survived them!