You can open a JISA for your child by tapping on 'Junior Stocks and Shares ISA' on the home page within the app and follow the onscreen instructions.
There are an extra few rules to consider:
You must be the parent/legal guardian of the child.
You must be 18 years of age or over.
Your child needs to be a resident in the UK or a dependant of a UK Crown servant.
Your child must not already have a Stocks & Shares JISA or a Child Trust Fund. If this applies to your child please see our article “Junior ISA: My child has a JISA elsewhere, how can I transfer it to CIRCA5000?" if you'd like to open a CIRCA5000 JISA for your child.