hey man i have some questions, im new to the site

but my question is that i have the same 5.5 gallon tank and its freshwater rite now with some baby mollies from my bigger tank and i really really really want to convert it to a planted tank i have filter,light,and heater and u know regular stuff like rocks, decorations etc. but i want to know what else i need and how and can i use the same water just put it in a bucket and pour it back in after the process??? pleae helpppp