There are helpful contributions above from @BOOM, @thinking_hydrogen, @Eden and @AJHY, great to see community members helping community members. Just to help remove the confusion, the most helpful official webpages are:
NewRegister (See “How customers are protected?”)
Keeping your money safe (See “Freetrade is part of the Financial Services Compensation Scheme”)
It is worth keeping in mind that, while you are protected under the FSCS scheme as detailed on the Keeping your money safe webpage, your investment might fall as well as rise due to movements in market prices and any such fall wouldn’t be covered by the FSCS.