Well sure there are many programs available out there ...you didn't mention what template it is so I will gest it is HTML/JS/CSS ...if it is CMS template you will have to use IDE and set some dev enveroinment
If you are good with code than you can use anything from simple editors .. notepad++,sublime text..or IDE like netscape but I suppose you aren't otherwise you would know what tools to use...so I would suggest to go with some drag/drop editor with GUI..you can check bootstrap studio,simbla...or just google free drag/drop editor...
Now again if you have template for some CMS than you'll have to look for IDE ...codeanywhere offer cloud IDE ...there is free plan also....so.
It is very hard to suggest you anything without knowing your level of knowledge...what template it is...again I gues it is HTML/CSS but you probably know that just front end theme will not do the job...you will need something as backend .
Now you can sign up for codeanywhere free plan and you can run one VM ,it very eas to set dev. environment in few minutes....and you have everything you need...