There are multiple ways for you to voice your opinion to your legislators.
You can submit your thoughts on a bill to the Committee hearing it before the date of their public hearing. This website, the MAPLE platform, focuses on this mechanism.
You can attend a public hearing for a bill of interest to you and sign up for a slot to speak before the Committee.
You can contact your legislators any time by looking up their contact information on the MA Legislature website. Your voice will probably carry the most weight with the House and Senate representatives of your own district, but you are free to contact Committee Chairs or any other member of the legislature with your opinions. You could request a meeting in person.