You can follow these steps to start investing in the funds of your own choice:
On the App
Home page → Mutual Funds (either from the center of the screen or from the bottom tab) → Click on the goal in which you want to set up the SIP → Invest. → Custom Funds → Start SIP
On the Website:
Click on the Invest button beside the goal of your choice → Custom Funds → Start SIP → Enter the SIP date, duration → Search for funds → Enter the amount (for the funds) → Review and Confirm. (YouTube link for reference)
You can also refer to these screenshots to guide you:
1. Click on the Mutual Funds section.
2. Click on the goal in which you wish to invest through SIP.
3. Click on "Invest".
4. Select "Custom Funds"
5. Select "Start SIP".
6. Enter SIP Details (Amount, Date, Duration) > Use the Search bar to find any funds > Enter the Amount.
6. Review and confirm
Note: If you have already invested in some funds and are looking to further invest in the funds, you will see those funds on the "Recent" tab. You can simply add the funds from this tab and proceed.
You can also click on the existing fund from your portfolio and click on "Invest More".
If you wish to check by when your investment will get processed or reflect on your dashboard, you can refer to this FAQ.
If you wish to add/remove funds (or change amount) in your existing SIPs, then you can refer to this FAQ