If you have shs certificate, you can enter the ghana armed forces. Follow this steps.
Buy GHANA ARMY recruitment forms which comes out every year around may/june
You can purchase the forms from any regional post offices and some banks like ghana commercial bank.
The forms price increases every year so you must have between 60-100cedis just incase the price increases so much.
After buying the forms, you fill it and submit it though the post offices or through any of their recruitment centres.
You wait for the forms to be processed and see if you get listed. If you get listed, you will under medical examination to determine your health status for the army. If you pass, then you will undergo 6months training to become a petty officer and then from there you are a full fledged soldier of the motherland. God bless Ghana.