Hope you can share with us the following:
Do you have a :ATMOSPHERIC, Vertical, cylindrical, flat bottom tank ??
Diameter ?
Height ?
corrosion allwance ?
Seismic ?
Type of roof : cone, floating roof ..?
Wind speed ?
Liquid density ?
material ? what is your Minimum mean day temperature to check material selection

But be aware that:
PVelite is for pressure vessels, heat exchangers, columns, drums according to ASME VIII , EN...
Storage tanks ( ATMOSPHERIC, Vertical, cylindrical, flat bottom ) are according to API 650 one of the software you could use is TANK (produced by PVelite owner).
You can also design a tank by hand calculation or bymaking your own excel sheets, probably you can find in this site some suitable excel spreadsheet for this purpose.
Tanks are limited in design internal pressure (very low not higher than atmospheric).

Tank are thin walled structure the wind and seismic are somewhat different to conduct than Vessels, further you have to select the thickness of the annular plate and design the roof as a structure when it is not self supported (within the limitation given in API 650).Checking for vacuum and adding stiffeners is also a special feature for tank (API has it is own rules). Also API 650 has other rules about testing and radiography ...

For your case calculate the empty case, the hydrotest case , the seismic case and check if you need anchor bolts or not. Give the loads ( H, V, Overturning ) to the civil for sizing the structure, estimating the settlement, design foundation if needed.

Do you have a :ATMOSPHERIC, Vertical, cylindrical, flat bottom tank ??
Diameter ?
Height ?
Type of roof : cone, floating roof ..?
Wind speed ?
Liquid density ?
material ? what is your Minimum mean day temperature to check material selection