Project involving Wifi

How can I capture the signal strength of my wifi connection using BoltIot device?

I’m not sure if the Bolt IoT module has any APIs to implement that.
The ESP8266 has commands to carry out this via AT commands.

Can you please explain?

Your Bolt IoT module is actually an ESP8266-12E module that is loaded with a firmware by the Bolt manufacturer. This firmware helps establish connection to the Bolt cloud by execution of the instructions on ESP8266 hardware.

The APIs defined for accessing the Bolt cloud can be found here.
There seems to be no API defined to collect WiFi details from the ESP8266 and send it to the Bolt cloud. So unless the Bolt cloud maintainers and firmware developers build the feature, you cannot get the WiFi details using APIs.

Although I haven’t tried this, you may use a serial to USB converter such as FTDI FT232 devices and connect it to the serial port of ESP8266(Bolt Module) to access the WiFi details using AT commands provided by Espresso. This might not work if the Bolt IoT module circuit prevents the ESP8266 from booting into AT mode.
Warning: I do not recommend nor endorse doing this.